Intake and Nikki Modding
 

Well the recent thread on hoggin a Nikki, and my own research that I've done for the past who knows how long has finally pushed me over the edge to take these mods for a spin.

First things first, I'm using one of my spare intakes and carbs here so I'm not compromising my main set up in case I ever wish to go back.


Now for the work:
I've already started on the intake which is an FB model. So far I have removed the shutter valve, anti-afterburn #2 fitting, and soon the auto trans fitting. I've also cut and smoothed the channels which seem to be a fairly common mod after the butterfly is removed. From what I've found, I will not be 'polishing' the runners and instead I just cleaned up some of the worst spots left from the casting process. The outside is still being cleaned, but once all is done with that, I'll start plugging the holes that are no longer needed. I also figured I'd round out the secondary runner for the rear rotor, as due to the situation with the shutter valve, the cast has a near 90 degree angle right below the mounting face that surely can't be doing anything beneficial now that I have the channels.

Here's a couple picture of progress so far:

https://cimg3.ibsrv.net/gimg/www.rx7...a15a525eb9.jpg

https://cimg5.ibsrv.net/gimg/www.rx7...304afabbb4.jpg

https://cimg1.ibsrv.net/gimg/www.rx7...5011ca884b.jpg
There's the '90' I was talking about. And when I said round out, I really meant fill.


As for the carb, I'm planning on doing mech secondaries, the supporting AP mods, trimmed boosters, slimmed throttle shafts, tapped airbleeds, and of course custom Venturi's (probably some other things that have slipped my mind at the moment too). I've got a friend that's setting up a new CNC lathe in the next couple months that I'll be using to make Venturi's from scratch. My hopes is that in using CAD, I'll be able to repeatedly make identical or slightly modified iterations. While I don't have a flow bench, maybe someday if I get access to one I could tackle the ultimate Venturi and throw the file up for the masses. Just a thought... ;)

If anyone has any gripes or helpful information, throw them on up here. I'd love to hear some input.

I'll be updating this as I make progress.

The intake is completed (minus reinstalling the brake booster fitting). I ended up plugging all the holes that I didn't need except for the runner end of the auto trans hole. I did the outside end first by mistake and I didn't feel like I could get the other end compressed enough to hold firmly. It would have been a marginal change at best, so better safe that sorry - I know I wouldn't want a chunk of resin flying into my engine.... All the other holes were either shallow enough that I could get the epoxy to fill all the way and stick to the sides, or they had another open end that I could push a rod through to help compress it. For all of the holes I could get to, I cut small notches into one or two walls, so if the plugs come loose from the metal, they'll have a little bump to prevent them from falling out. Had they been perfectly cylindrical like most of the holes were, they could have just slid out if they somehow worked loose. I used JB Weld Steelstik for everything, and while I was impressed with it, the stuff hardens so quickly that you've got to work fast. The only thing I'm worried about is their adherence, which is exactly why I cut the ''bumps'.

Enough explaining, here's some pictures.

https://cimg0.ibsrv.net/gimg/www.rx7...bf049c0119.jpg

https://cimg4.ibsrv.net/gimg/www.rx7...89540aba27.jpg

https://cimg0.ibsrv.net/gimg/www.rx7...bdef211bd7.jpg

https://cimg1.ibsrv.net/gimg/www.rx7...14912b05db.jpg


And then a couple of cleaned up photos too...

https://cimg6.ibsrv.net/gimg/www.rx7...3c1027aa00.jpg

https://cimg8.ibsrv.net/gimg/www.rx7...a9c6682fff.jpg

I'll probably get this installed either later this week or the following weekend.

Next up is the Nikki work. I've got a couple options: I have a complete SA carb that is extremely dirty and rusty (no clue where it came from), and then a 83+ carb that is clean but missing a T-body because I installed it on my '82 carb so I could have vac advance. That said, I still have the '82 T-body but it doesn't have vac advance. What ever carb I build it will be a permanent assembly in the sense that all the parts will belong to that one carb and will not be switched around again. This is still a DD, so vac advance would be nice for mileage and around town. How much of a hit do you think part throttle power and mpg would take if I skipped the vac advance? I do realize that being modified, mileage will take a hit regardless.

Thoughts?

JB Weld will work fine, don't sweat it too much.

Don't mix carb and throttle bodies, use the same from the same year, there are small differences that can get you at tuning time because some hole or another doesn't line up.

Not true. Only SA and FB differ in any significant way. But regarding the differences between 81-82 and 83, vs 84-85, those are the three groups in the FB production run and the main difference here is the richer solenoid circuit that the 84-85 had which earlier models didn't have (unless you go back to SA, which had it). It was a pressed in jet in the 84-85 baseplates. There was a corresponding hole and a solenoid between the secondaries unrelated to them as it connected in a Y arrangement down at the primary barrels in the baseplate. Also there were some air bleeds at the top of the main body which controlled, well, the air. The solenoid was activated at idle to allow a richer mixture to maybe warm the cats up quicker for emissions purposes. Regarding 81-82 to 83, there was only one major difference allowing you to tell them apart. 81-82 had a 12mm nut on the OMP lifting lever side of the primary shaft while the 83 and later had a 10mm nut there. I don't think there are any holes that differ between these groups.

Interesting... When I did the T-body switch I checked all the holes for alignment and both were identical other than the omission of the vac advance hole in the 82. There was probably that pressed in jet too, although I'm not positive. I do remember the throttle shafts being slightly different in terms of the way linkages mounted and also that there was a different sized nut on one. I want to say that one also had a smaller shaft than the other, but I might be crazy. I'll take a look at them next chance I get.

The 83+ carb that I have does contain an extra jet and also a plug below the triangular protrusion (opposite the fuel lines) of the airhorn, is that what you are referring to as part of the richer solenoid circuit? I remember the one on the SA carb I ran, but this carb doesn't have the solenoid. Oh wait a second, I just remembered I had a friend tear down this carb and he may have removed it, although I honestly don't remember. This carb also has the newer style vent solenoid - the one where there is only one visible wire and it is either threaded or pressed in as opposed to using the triangularly arranged screws and bracket.

And to update my non-posted post....

The carb does have the spot for the richer solenoid. Here's a picture
https://cimg2.ibsrv.net/gimg/www.rx7...13306eebc2.jpg

And here's a photo of the vent solenoid I was referring to
https://cimg2.ibsrv.net/gimg/www.rx7...d2adbb03f6.jpg


I still have the richer solenoid although since I'm not running emissions parts anymore, could I just plug the circuit? This is where I wish that I was modifying my 82, just because it was simpler from the start :). Anyway, I'm not gonna mod the 82 since it runs reliably as is.

So from what you've said, it sounds like this is an 84-85 carb. The question remains though, swap T-bodies again to keep vac advance, or do without it. I guess another angle to look at is that the modded Nikki will already be harsher on mpg, so perhaps I should keep the current one as is so that I can always go back to my good mpg build if I desire, rather than averaging the two together and making neither outstanding. Does the vac advance really make much of a difference down low/part throttle? I know I didn't notice much of a difference when I added it a while back so.... Who runs it and who doesn't, and what logic do ya have to support the decision?

Thanks thus far.

Ah yes, I don't think in terms of vac advance but indeed there could be one additional hole for it. Maybe, I'd have to look. There are two nipples on the baseplate that have a timed vacuum function but I have not explored them yet.

Adding to what I mentioned earlier, the 81-82 shaft is slightly shorter on the throttle lever side but a couple mm, compared to 83-85. The 83-85 shafts, being slightly longer, are easier to work with when doing custom linkage setups for project cars.

83 was the first year for the single wire smaller body vent solenoid. It is threaded into a larger pressed-in brass housing. To gut these, I grind out the nylon valve with a narrow dremel bit, then break it off with short needle nose plier, then remove the small spring from the solenoid and cut the wire (so you won't have to keep the trigger wire in your rats nest wire bundle if you choose to de-loom, but it can be handy to keep). Then thread the solenoid in with the same crush washer or a new one from a rebuild kit.

If 82 and older with the larger body and three screws, this can be fully removed and a flat aluminum plate added with the triangular gasket from a rebuild kit. Or make your own. you have to make the aluminum cover plate anyway...

Yes you can plug the circuit. I like to use a piece of aluminum rod and drill the hole slightly smaller than the diameter of the rod. This is the hole at the underside of the main body sort of in between the secondary venturis. Then I use red loctite and hammer the rod in there using a center punch tool. The richer solenoid can be kept with the spring loaded rod, or remove the hole thing and fill with quicksteel. I've done it both ways. I do keep the air bleeds above just because there is direct communication with the float bowl to the left (rear side of carb when installed). You will see the machined holes in the float bowl and corresponding circuit pathways outside of the main body. Oh and I do clip the wires on the solenoid if keeping it, to discourage anyone from thinking they still need to be connected on the 84-85 cars.

So the deal with the timed vacuum nipples is that the second to front one on the '82 deadheads on the transition from the baseplate to the T-body. Normally there would be a hole that would continue from the baseplate to a slot just above the front primary butterfly. This hole and slot are missing on the '82 for whatever reason, and as such the second to front nipple goes literally nowhere - it had confused me for the longest time until I took it all part to see if something was seriously clogged. Normally there are two timed slots in the front primary, one that is about level to the closed butterfly, and one just above it set off to the side a bit. Now that's just from memory, so I may have mentioned something off by a little.

As for the longer shaft, it sounds like the benefit is negligible being only a couple mm. Does the extra length really come in use when making custom linkages? As in, is it worth swapping back just for that (omitting the vac advance part of the equation)? I'm also trying to keep the car on the road while I'm doing this work, so swapping would mean more time down time (I swapped linkage parts around so that I could use the SA TPS, although that's getting removed now that smog equipment is gone). You know what, I just remembered that in switching parts for the TPS, I swapped over one shaft and not the other because there was some sort of matching issue. I think I swapped the primary shaft and kept the secondary in the original T-body because the SA TPS sensor linkage wouldn't mount to the later shaft. So in theory, on my bench I have the '82 T-body and its secondary shaft, and then the 84-85 primary shaft. Got to love it when parts get all mixed around... Are both later shafts longer, or would this arrangement work just fine?

I think I'll keep the vent solenoid for now since for the time being I'm still running the PCV and related components.

I'm also doing away with the altitude compensator. I'm assuming that I can just install a block off plate and not worry about the jet and two other holes? Any reason to, or to not block them off? I figured I'd also remove the two fittings up top for its vacuum lines and then just plug the other ends where ever they go - the carb is fully dissembled minus the jets so I don't know where that would be at the moment.

And for plugging the hole with the aluminum rod, I'm assuming you meant the hole that goes from between the secondary venturi's (as you said) and then is angled up towards the center of the carb where it then meets with the richer solenoid valve? And yes, I just checked the float bowl and I see the two holes and circuit pathways you are referring to for the jet. Speaking of jets, I just removed the brass plug that's next to the richer solenoid jet, and I noticed what looks like a weight. I took it out and there's no check ball below it. Was there supposed to be one?

Oh so many questions...

Normally the second nipple on the carb spacer has zero vacuum at idle and shows vacuum when the throttle is actuated.

Don't swap it. I was mentioning it anecdotally only. The extra length makes installing the 12mm nut a little bit easier if you've just done anything with the linkage. But the 81-82 shafts are still fine to deal with because, and you have to really ask yourself, how often does anyone ever do any linkage work? Next to never.

I cut out a 1/4 aluminum plate for the alt comp removal and make a gasket for it or use the OEM one in a 12A gasket set from Mazdatrix (yes the OEM Mazda gasket set for N201 has a beige colored carb gasket among other gaskets in there for whatever reason). Then I take out the 40 stamped air bleed under the air horn and fill it with solder from the back side (in case the solder detaches from the brass, it can't fall into the engine). There is virtually nothing to be done about the two vertical holes next to the booster that communicate with the alt comp. Some people have hammered check balls into them but I don't like that idea as it creates a space that water will get into and can't come out of if you ever have to wash the carb in the future. I've tried using full length phenolic inserts from SA carbs (instead of the castellated nylon ones found stock in 81-85 carbs), but sometimes they don't fully block off the internal diagonal holes. But I can tell you if you manage to block off even one of them, through a series of means at your disposal, the carb will have a more stable transition circuit if you are going with larger venturis than stock.

The altitude compensator circuit is intimately linked with the primary circuit through the primary booster / air bleed / emulsion tube by way of the small diagonal holes and the vertical holes that connect with the air horn. And this is also linked to the primary transition circuit and the primary idle circuit. It is all one big mess and can cause issues.

No check ball below that brass weight.

Indeed there are a lot of questions and secrets about these carbs that even I am still learning.

So it sounds like I'm staying with the T-body I've got now - '82 casting, no vac advance, '82 secondary shaft assembly, and an 84-85 primary assembly.

As for the block off plate, I'll probably just make a gasket with some of the roll paper I've got lying around, and cut out a new plate when I do the ones for the intake.

It would seem like I could just fill those holes by the booster with JB weld again like I did in the intake with no ill effects..? And I had actually been referring to the two brass hose fittings on top of the airhorn/altitude comp. I know the '82 doesn't have these fittings, and perhaps the '83 doesn't either. They might just be an 84-85 thing, I honestly don't know. Regardless, if I understand correctly, I should plug everything related to the altitude comp that I can, yeah?

And thanks for confirming the lack of a check ball.

For now most of these questions I'm asking are conceptual as I haven't had time yet to start diving into the carb. As no carb that I have worked on to this point has had these 'features', I'm really just working with the short time I spent while taking those photos. I'm sure this will all make better sense once I start messing around with the carb.

The holes by the booster? I don't understand.

Brass hose fittings? No those are steel. One has a tiny air bleed pressed in made of brass. They are an 84-85 thing only. Yes, block them all off.

My bad, I think read that wrong - particularly considering that these sure aren't vertical... Anyway, I was referring to these two holes:
https://cimg2.ibsrv.net/gimg/www.rx7...3a99003c7e.jpg
Which holes had you meant?


And yes, the steel hose fittings; seems I just had brass parts on my mind...

Jeff your everywhere with your mad scientist info ! Great

Just a quick progress update.

I made the split air block off plate today and sometime here I'll make the ACV one - I'm planning on installing the intake Sunday or Monday.

Also got the boosters started and I removed all of them without any damages - I used the taped pliers method as I don't have enough spare airbleeds to destine one as a tool.

I only had a little time this afternoon, but I started cleaning up one of the secondary boosters. The centering tab removal was a success, and I started to make the airfoil shape on the support arm. Unfortunately the Dremel sandpaper wheel I was using to remove the casting line was more aggressive than expected so this isn't the prettiest one. Although this is my first one ever (and it's not nearly done yet), so I'd say I'm headed in the right direction. I've only done a quick polish on the side facing the camera and I'm planning on going back and smoothing things out a little more with some higher grit paper before I'm done. Here's a picture of it so far.

https://cimg4.ibsrv.net/gimg/www.rx7...9d3441181e.jpg

I don't think you can see it in that photo, but the worst carnage from the grit wheel are some minor low spots that won't level out. They're almost unnoticeable, but they're there nonetheless. I've been doing the sanding by hand since that incident. I'm also not sure what to do about the inside, other than just clean it up - not really seeing a way or a reason to get a polishing bit in there.

Doubt I'll get to work on anything again until Sunday, so expect an update sometime around then.

Well I'm in the process of swapping intakes. I haven't removed the old one yet as I still have to drain the coolant, although when looking at it after removing my ACV block off plate that I'm reusing, I noticed the exhaust check valve. It's missing in my other intake and I'm debating whether there's any point in trying to move it over. Seeing that with the block off plate that exhaust isn't going anywhere anyways, is there any logic in having it as a second means to stop the exhaust gasses from potentially making it past the block off plate? Personally I would say no, but I figured I'd throw it out here for opinions.

Here's a picture of what I'm referring to:
https://cimg7.ibsrv.net/gimg/www.rx7...caa444006f.jpg

Well yesterday I didn't end up switching over that check valve, although I still could if there's a reason to.

Anyway......... The intake is installed and dang is the car smooth. Here's just a quick rundown of everything I did on the intake: removed shutter valve, cut rear rotor runner's channel to match front (essentially making it SA style), ported both channels, filled original rear runner 'mix hole', filled 90 in rear secondary to smooth and match runner profile, filled all vacuum holes other than the brake booster, removed casting imperfections, ACV delete, and #2 anti-afterburn valve delete.

A few weeks ago I tried disconnecting the vacuum signal to the #2 anti-afterburn valve and I found the car backfired much less. The line from it to the rats nest had been plugged for some time, but as I didn't know for certain how it worked, I reconnected it the other line that goes to the T-body. Yesterday I fully deleted it thanks to the hole on the intake being plugged, and wow did it smooth things out. You used to be able to hear it if you would rev or run up in the rpm's and then let off quick (it was a sort of 'cht cht cht cht...' sound), and now that's gone. I also used to get a lot more pops and burbles when shifting and now it's practically silent so that's cool I suppose. The overall intake mods seem to have not only improved power (according to the seat Dyno), but most definitely responsiveness and smoothing of the powerband. First gear doesn't last long enough for darned near anything now (pretend this text is a wink because I ran out of photo space). The car also sounds much different, particularly on start-up.

Speaking of the exhaust, I replaced my muffler gasket yesterday so that probably contributed some to the sound too. Here's a picture of how bad the leak was (and yes this old gasket was reused from my parts car because I didn't anticipate having to order it from RB or Mazdatrix at the time):

https://cimg7.ibsrv.net/gimg/www.rx7...a7993865aa.jpg

https://cimg7.ibsrv.net/gimg/www.rx7...c2e29d0e65.jpg

Ironically, this gasket is the OEM size and yet unbeknownst to me until yesterday, I have the larger 'RB' sized pipes and flanges. The sealing rings on this old gasket weren't even touching metal - no wonder it's in such rough shape. The internal material is also completely missing and it turned my new bolts black in that area.

https://cimg5.ibsrv.net/gimg/www.rx7...de9ac8697a.jpg

Here's a quick size comparison between the two gaskets:
https://cimg8.ibsrv.net/gimg/www.rx7...1fe7b970f5.jpg

So now I'm really curious as to what muffler I have. It's dual pipes in and out, bare metal, and really low profile. The pipes running to the tips are painted black and then the tips are chrome, angled back from top to bottom, and have perforations on the inside sorta like a glass pack. No markings or identification that I could find. I doubt anyone would recognize it, but you know, there's a chance.


Removing the old intake was also rather odd because my ACV block off plate and gasket were covered with what looked like oil. Not on the outside, just the inside, and this 'oil' was actually sitting in the split air part of the ACV intake holes - not the exhaust. No clue where it came from, although I feel like it might be condensed water that was never allowed to escape. Strange nonetheless.

Here's a picture of the oily stuff:
https://cimg2.ibsrv.net/gimg/www.rx7...efde935b83.jpg

And finally a picture of the installed intake:
https://cimg3.ibsrv.net/gimg/www.rx7...3b7c74cf7c.jpg


Today I'm changing belts, figuring out what is clicking under my dash at idle that I can remove or fix, and working more on the performance carb.

Well I'd say it's about time for another update.

The car is still running great, and so far I'm quite pleased with the intake work; no drawbacks to be found. I've started some more work on the carb, nothing major (I have yet to start on the linkages), but the boosters are coming along and I've been cleaning up the main body and air horn.

Here's a couple pictures of a finalized secondary booster. It's not perfect, but I'd call it good enough.

https://cimg4.ibsrv.net/gimg/www.rx7...51df6166ef.jpg
https://cimg2.ibsrv.net/gimg/www.rx7...045ed3c009.jpg
https://cimg3.ibsrv.net/gimg/www.rx7...b51dc9aa8f.jpg


Most of the work I've done on the carb so far is just cleaning. I did find the right bolt for the primary booster (to remove it that is) and it's an M7 x 1.0 thread. I think the secondary is M9 x 1.0, although I have yet to come across a bolt of that size. The carb is fully disassembled and the rebuild kit just came in a couple days ago.

So now for a couple questions:

1. I've seen in a few threads that people drill out both the AP nozzles and its banjo bolt. Is this recommended for going to mech secondaries, or is it more so for the combination of mech secondaries and larger venturis? The mech secondaries are happening now, but the bored venturis are probably coming this summer. So the question is, should I drill the AP bits now, later, never, what?
2. I'm starting to think about removing the vent solenoid - contrary to what I had said before. I'd also eventually like to get rid of the idle compensator and the rest of the rats nest (the idle compensator is really the only thing left other than the purge system). Are there any negatives in removing either? The idle compensator is basically a 'vacuum leak' that opens up once the car is warm and considering that you are suppose to tune the carb with that line plugged, I don't see any immediate harm in removing it. Thoughts? I know it's been done, there just doesn't seem to be much documentation on it.
3. What is the best way to go about cleaning up the PCV system bits? Just plugging it would lead to water being trapped in the filler neck - I don't need more rust, and most definitely not in my oil - and I can't really figure out a good way to simplify it. This project is partially performance, partially tidying things up. Being that both the idle compensator and PCV are supplied by the same vacuum source, removing the idle compensator would be a step in the right direction, but what's the best way to clean up the remaining lines without screwing anything up?

That should be it for now. Once I finishing cleaning parts and actually start work on the carb there will undoubtedly be more questions and updates.

1. Don't follow any advice about drilling the nozzle and the banjo bolt until you have test driven your carb with all the mods. Then try drilling them a tiny bit larger than stock to start. What ever you do, never drill them as large as recommended by others. The stock size is tiny, like .4mm or .5mm. I've seen a racing one with a 6 stamped on the bolt head indicating .6mm. I usually go for a .90mm to a 1.20mm but never any larger and it depends on what the carb will be used for.

2. The biggest problems with stock carbs regarding stability is all the excessive amounts of air they let in through air bleeds and controlled vacuum leaks. It's all so the choke system will function as intended. Because I remove the choke flap due to how restrictive it is, I've been able to also reduce the excess air and end up with a vastly better carb. So to answer your question, it is an ongoing process of trying things and observing the results.

3. There are various ways of dealing with PCV. The OEM system only had a purge valve that was tied into a lot of other systems. It can be replaced by an aftermarket PCV valve and hooked to the middle nipple on the phenolic spacer as this one flows pretty much equally to both primary runners in the manifold. Study the spacer and you will see that it has a Y shaped channel. But you may also need to add a tiny restrictor somewhere in the line, depending on the results.

First off, thanks for the good info as always.

Second, I've been contemplating removing the choke system (keeping the fast idle though). Being up here in Oregon, where just a few weeks ago we were seeing temps in the 20's, I'm a bit worried about cold starts. I was thinking I could just try without it for a couple days - or one test if I can't get it to start - and then reinstall it if it doesn't work out. The issue I'm seeing right now is temporarily, and potentially permanently plugging the holes for the choke flap rod. If I try without the choke and it doesn't work, I'd like to be able to reinstall it, but just leaving them open is surely no good for debris getting into the carb. In all the threads I've read so far no one mentions plugging the holes. I'm assuming that either this is just assumed to be done by what ever method someone wishes or that they're left open. Thoughts on this?

Also I've been doing some more poking around the altitude compensator system and it seems like I can plug all the holes no problem like you had said a couple posts back. And don't take that as a challenge on your info, I just like to fully understand things before I start throwing the JB weld around. I'm still doing research and investigating (not to mention cleaning) but I'm getting progressively closer to the mod and reassembly stage.

I've got a few more questions floating around in my head, but I think I may have confused something up there and so I'll post with those when I'm looking at the carb again.

So I think I figured out what holes you were talking about Jeff. I probably just severely misread your post 'cause I don't know how I missed these. In the photos below I'm referring to the two vertical holes that run in the divider between the primaries and secondaries (next to the boosters like you said originally).


https://cimg0.ibsrv.net/gimg/www.rx7...feb85d02e8.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...68ec15b973.jpg

So from what you said, and my own investigating with the air compressor, these holes go to the primary main airbleed / fuel jet cavity. What makes them so difficult to block off? I can see where the diagonal holes were drilled to connect these 'tubes' with the airbleed area, but wouldn't just blocking off the tubes themselves solve the issue? Or do the diagonal holes need to be blocked off too? Is that why you use the SA "phenolic inserts"? I know I'm repeating a bunch of what you already said, but I'm just making sure I've got this right. I have an SA carb that I'm using as a parts carb so I could swap those in no problem.

Also by phenolic inserts I'm assuming you mean these things, and that by full length you meant the SA ones don't have those feet:
https://cimg4.ibsrv.net/gimg/www.rx7...a719df4e1c.jpg

Also, if water is a worry, wouldn't it just work to plug both ends of the passages on the air horn? That way water could never enter a sealed part of the circuit, and the SA inserts would just be an extra precaution (also no water could get stuck in the body since there would be no permanent seals in it).

Right now that last combo I mentioned seems like the best option, although if there's some reason it wouldn't work out, let me know.



The previous post's questions still stand.

I believe that last post of mine warrants some rephrasing...

So if the vertical holes in the body were plugged, that would leave the connecting diagonal holes as a possible way for water to enter and get stuck in that part of the circuit during a wash. That's why you suggest not capping the vertical holes in the body, and rather advise running the SA phenolic inserts as they are a removable way to block off the diagonal holes. Being removable, there is no worry for potential water getting stuck in the passages. Although, you also mentioned that the SA phenolic inserts don't always seal completely and so...

As for my addition to that, both ends of the circuit on the airhorn side of things are easy to get to. If I blocked the vertical holes on the air horn, and then blocked the hole where they meet at the altitude compensator, that would provide a completely sealed circuit that no water could get into. If I did both the SA phenolic inserts and the aforementioned, surely that would be an effective way of fully blocking off the circuit without a worry of invasive water. Any unforeseen issues with that method?

That's what the last post was aiming to convey; hopefully that made a little more sense.

Boosters are done!

I had taken a little break from them to do the carb cleaning (which now done too). Just finished the primaries last night. Here's a few pictures.

https://cimg7.ibsrv.net/gimg/www.rx7...30b994344b.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...3a9a310078.jpg
https://cimg4.ibsrv.net/gimg/www.rx7...0ef00eb4dc.jpg
https://cimg5.ibsrv.net/gimg/www.rx7...e004ea2240.jpg
https://cimg1.ibsrv.net/gimg/www.rx7...76eadc282b.jpg

I will say that the primaries were a little different to do as they have a 'two level' support arm. Due to that, there are a couple triangular spots on each side that show the remains of those supports. I didn't want to remove much more material from that area, and it should be better than stock regardless. For anyone who may copy those in the future, I suggest not cutting the angle into the left over centering arm on the primaries. It take a long time to round them out using mini files, and I seriously doubt there's much of a gain, if any.

As I alluded to up top, the carb body and air horn are done being cleaned and are now being checked for any blocked passages. I've made the altitude compensator block off plate and gasket, and the next step is getting a few peices out of my parts carb.

Still curious about the content in my past few posts.

The carb is getting much closer. Boosters are installing and centered, fuel jets and airbleeds are in, and really the only peices left before the carb can go back together are the AP mods, filling those passages (which Jeff if you could confirm that I'm not crazy, that would be appreciated), and figuring out what needle/seat/float/clip combo I want to use. As of now I've had the best luck with SA floats and the like, but I would doubt that the FB floats and such have any real issues (perhaps just the sets I have do...). Anyway, with my other carb I was always having flooding issues with the FB floats and I've got an extra set of matching SA floats, needles, etc. that I'll probably end up using - I'll see as the install gets closer.

I should mention that while I'm nearly done with the carb, the t-body hasn't been touched yet. I've still got to work out the linkages, thin the throttle shafts, and just some overall prep.

Here's a couple pictures of stuff as of now.

The body:
https://cimg2.ibsrv.net/gimg/www.rx7...a999ca4860.jpg

And the SA phenolic inserts just for documentation:
https://cimg4.ibsrv.net/gimg/www.rx7...519252fd57.jpg

Considering there aren't too many signal affecting mods yet (no Venturi hogging), I put in the SA primary jet (93 I believe) as it's a point up from the stock 84/85 primary. I left the secondaries stock as there were no year differences, and I went down a size on the primary no. 2 airbleeds (I think; I did this a couple days ago so I'm not positive which bleed it was or what the size is without going back and looking at it) by using the SA bleeds. This is really just a starting point right now as I still need to learn more about how the airbleeds affect different load and rpm scenarios.

I doubt I'll get much more work done until the end of the week, so stay tuned for more updates most likely starting Friday night or Saturday.

Good effort in documenting your work. As for filling passages you mentioned... What passages?

By passages I meant the vertical holes that are connected to the altitude compensator. The full explanation of what I meant is in post's #20 and 21. Post #20 explains it a little better, but both have some valuable content regarding the phenolic inserts and capping the vertical holes.

You should try the phenolic inserts first. Then install the boosters using the waxed finishing nail punch tool method to spread them a bit before you tap them back in place, and get them as centered as humanly possible. Then blow compressed air through the vertical holes and see how much comes through the boosters. You might be surprised to see that at least one of them is completely blocked off by the SA insert while the other just has partial flow. This will stabilize the primary circuit and is far better than leaving the stock nylon castellated inserts in there. If you experience issues, you could hammer a set of small ball bearings into the vertical holes but I don't think you will need to seeing as your venturis are still stock 20mm. Once you get to larger venturis, it can be a good idea to block them off more.

As for posts 20 and 21, I would no attempt to block the diagonal holes. That is a bit too iffy, even for me.

The the SA phenolic inserts are in there, and next chance I get, I'll check if there's any flow to the vertical holes. As for spreading the booster a little before install, well... I had read that in another thread and had actually planed on doing it, but then when I went to install the boosters, they were practically the perfect size. After I tapped them in (making sure they were as centered as I could discern), I used the bolts I bought as removal tools to check and can say with confidence that they are not going anywhere. I also purposely avoided using any grit material when cleaning the sleeve part of the boosters for the exact reason of potentially making the boosters looser.

As for finding another way to block the diagonal holes, I had never planned on that - too iffy like you said. Rather I had meant blocking the airhorn side of the vertical holes. I'ma go grab some pictures of what I mean quick...


And we're back. So in the below pictures of the airhorn, the two vertical holes (circled red in the first picture) are the continuation from the vertical holes in the body. These holes then run to the where the altitude compensator mounts and join into one hole (circled blue in the second photo).

https://cimg2.ibsrv.net/gimg/www.rx7...753c3aeb4a.jpghttps://cimg3.ibsrv.net/gimg/www.rx7...b8ff116378.jpg

So my question is, assuming that the gasket between the two parts of the circuit is doing its job, would filling both the alt comp hole (blue) and airhorn vertical holes (red) provide a solid means of blocking off the circuit without any worry about water getting stuck somewhere (the problem with using check-balls or similar in the body's vertical holes)? I'm still using a block off plate for the altitude compensator, but if I sealed both ends of the aforementioned circuit, it would seem to be a good way to achieve a completely leak free (both for air and water) way of sealing that circuit. When I was asking you to confirm whether or not I was crazy, the above is what I had been referring to.


Also I should mention that I did some minor clean-up on the airhorn too. There are some casting marks in the primaries that I removed and there were a few other bits I tidied too. Again, probably not worth the effort, but this carb is going to be 'perfect' if it kills me... well maybe not kills me, but danged close to that ;).

The questions concerning a removable solution to plugging the choke flap rod holes are still up for the answering. And to go with that, what temps would you consider it reasonable to DD a car without a choke?


Oh and one more thing. This just popped in my head, but would it work to use the richer solenoid as a sort of 'electronic choke'. I know it's not at all the same thing, but perhaps it would make Oregon morning cold starts a little more dailyable? I haven't really looked into it yet, just a thought.

Ok, that sounds reasonable about blocking the vertical holes in the air horn only which allows you to clean the main body at a future time with no worry about water getting trapped. I blocked those holes in one main body only because its top is exchangeable with other carbs I test. This made more sense for me to do at the time.

When you correct the idle air imbalance that stock carbs come with, by reducing the air bleeds from stock FB 170 or SA 150 down to 120, it allows you to easily start the engine with no choke flap. Temps range from freezing to 100 degrees F at least. You have to understand the factory intended for the car to have a choke and for the whole system to be calibrated for it, which only allows the carb to run well within a narrow temp range. By changing the size of those air bleeds, you are increasing or decreasing the range within which it will run well. In this case making them smaller increases the usable range with no negatives as far as I know... other than the choke flap becomes useless and restrictive. Well, it's always been restrictive.

I tried that idea once. It is an imperfect seal and was leading to a condition that made me realize it was leaking just enough to produce an inconstant tune at idle. I watch my wideband like a hawk. That solenoid also seemed to be incompatible with boost.

I think you are worrying too much about cold starts, but I understand where you're coming from ie this is new territory and you're open to learning things and covering your bases.

This leads me to my next thought. The 93 jets from an SA you swapped in strikes me as a good idea for now, but just understand that by reducing the idle bleeds like I'm recommending will allow less total air into the primary circuit as a whole. Thus swapping in richer jets might make it too rich and maybe what you want are a set of 91s until you hog out your venturis. What I'm talking about is all three primary circuits: idle, transition and main are intimately linked and one will not function without the other two being there. It isn't like a weber where the mains are swappable while idling. I've tried idling a Nikki without the main air bleeds or the transition bleeds in place and it was a no go.

I'm not sure how well I explained any of this. Does it make sense?

I'd say you explained it well. Just for documentation sake, here is the current jetting load-out:

Primary:
- Main air bleed: 70
- Slow air bleed no. 1 and slow jet: 70/46
- Slow air bleed no. 2: 150 (stock: 170)
- Fuel jet: 93 (stock: 92)

Secondary:
- Main air bleed: 140
- Slow air bleed no. 1 and slow jet: 160/(110 or 120?)
- Slow air bleed no. 2: 60
- Fuel jet: 160

As for that secondary slow jet, I think I may have mixed them up, which is really unfortunate because it's the only jet that I can't find a stamp on. It looks like the SA's were mostly 120's and most FB's were 110's, and I took at least one jet from an SA and the other either came from another SA or an FB. Both jets are the darker grey color (I believe some variations are also a brass tinge), but it's the lack of markings that's got me worried. Are there markings on these jets and I'm just blind, or did the stamps just get left off of these for some reason? The reason they're all switched around is due to two of my parts carbs having half of the head stripped off on only these jets from who ever rebuilt them before me, leaving me with two unpaired jets that I made the unfortunate mistake of not labeling. Is there a good way to check the size, does the finish mean anything helpful?

For going down to a 91 with the 120 bleeds, yeah, makes good sense. I'm not sure if I'll get the main air bleeds tapped before the carb is ready for testing, but when I eventually do I'll be sure to heed that advice. Speaking of tapped air bleeds, would I be wrong to assume that you drill the orifice out of the stock air bleed? Or do you just leave it alone and use the holley bleed on top of the factory one, which seems like it would compound the jets emulating an even smaller jet?

Edit: Just realized you were referring to the no. 2 air bleeds with the 91/120 bit. The question about the tapped air bleeds still stands though.

And it sounds like blocking off the richer solenoid is just a better idea for the long run.

If worst comes to worst with the secondary slow jets, I can always take the set out of my original SA carb. Then again, that still won't solve the issue of figuring out what size they are.



Quick update (yes I realize I haven't posted this yet). I just went out and very carefully checked the size of the secondary slow jets with a caliper. I have doubts that the caliper is accurate measuring the ID of something so small, but the readings were ~1.00mm (100) and ~1.10mm (110). So I suppose that just adds to the confusion, which is just dandy...

Those two holes in the divider NEED to be plugged in some way. They cause some kind of a leak in modified Nikki carbs and the carb runs lean. I have those holes in my carb.



EDIT: oops I see you are using an FB top.... never mind. I think they only cause a leak if you are using an SA top with an FB body.

Mini-update...

Not a whole got done on the carb this past weekend as I've been pretty busy with other activities. However, here's what I did get done: filled air horn 40 jet with solder and installed, cleaned needle seats (perhaps too well...), and began cleaning linkages and other steel components.

The seats aren't exactly 'too clean', although they really didn't need to be this clean:
https://cimg1.ibsrv.net/gimg/www.rx7...47016724d8.jpg
I got a little carried away....

And as for those steel parts (brackets, linkages, and stuff), I have decided to go all out on cleaning them, which means I am actually going to be replating them. I did some research yesterday and set up my home-brew electroplating bath. Here's the first plated piece.
https://cimg5.ibsrv.net/gimg/www.rx7...898dde6281.jpg

Now you'll notice that it's still grey, which is due to the plating being solely zinc at the moment. I ordered some yellow chromate which will be here eventually, and that's what hardens the coating and gives it that OEM yellow tinge. It's a surprisingly easy process all things considered, and I'd say it makes sense for anyone going for an all out carb resto.

One quick question. Is there a benefit to removing the screens above the needle seats and instead running a second filter before the carb inlet? Besides easier replacement/cleaning, is there a benefit in terms of restrictions?

That's about it for now. More work will get done as the week goes on.

Yes it helps the flow some and is a common mod to these carbs. There is also some screens in the fuel inlet pipe connections that can be removed as well. I used to run a glass filter in my carb inlet fuel line for this reason. I've since stopped using it because it really didn't pick up anything but I change my fuel filter at least yearly.

Nice job cleaning up the carb parts. Ray will be proud of you.

Would you care to share what method and supplies you used to clean the parts and plate them? That looks great. I looked into doing this a while back for some brackets but ended up just painting the pieces after getting confused as to what to order, and how to dispose of the chemicals afterward.

Agreed on both things TG mentioned. The rotary gods will smile now.

Thank you for that confirmation. I thought I had seen it before so it's good to know I ain't crazy :).


As for the cleaning process, yes of course I'd be glad to share my methods. First off you need a source of relatively pure zinc - the more pure the better, although I doubt some impurities will harm much. I used some melted pennies (newer than 1982) as they are 97.5% zinc, and technically so long as you aren't profiting from the process, it's legal. Of course you could just buy a roll of zinc sheet from some outlet, but the pennies only cost me 20 cents and they were readily available. The other things you'll need are some sort of container to use as the bath (large enough for the parts you are doing), some white vinegar (5%), epsom salts, a scale, some electrical wire (~16 ga.), a sacrificial computer power supply, soldering equipment, an alligator clip, and some patience.

Once you have the above, create a mix of 1L of vinegar to 100g of epsom salts. Mix this thoroughly (some un-dissolved salt is okay). For the pennies, grab a surface that can tolerate the heat and have at the melting. I find that holding one end with needle nose pliers works well as you can heat the majority of the penny (although preferably apply heat so that the bottom relative to how you are holding it melts before the top) and then the zinc just falls out - no copper contamination. Once you have enough zinc (the more the better within reason), go ahead and combine them into two equally sized 'plates'. Mine weren't too plate-like, although as long as they are flat and have decent surface area, you'll be fine.

Get a couple wires cut that are long enough to connect between the two ends of your chosen vat. Solder one end of each of these to each plate. You should end up with each plate having one wire attached, preferably as far too a side/corner as possible as you won't want to submerge the soldered part in the solution.

Now get your power supply. If you have an adjustable bench supply, that'll work fine, but for those who don't, get that computer power supply and cut free all the yellow wires and grounds (black). Now I can't guarantee that your computer power supply will work (part of the reason it's sacrificial), but most should work fine - it really depends on how sensitive they are to 'short circuits'. The yellow wires are 12v and you'll want to connect those two the previously made zinc plates by a means of your choice (I used a spade connector). The negatives will connect to your part using the alligator clip, and I would suggest extending the length of the wires so that your PSU doesn't have to be right next to the vat.

Letting the zinc plates (anodes) sit in the solution for a little bit prior to starting will help prep it for the plating process as some zinc will dissolve into the solution. Although, when you are done plating I would suggest you remove the plates as they will eventually fully dissolve into the solution which you don't want. Next, your parts need to be really freaking clean. Have at it with the wire brush (I use Dremel attachments) and get that component clean as can be. Any rust, paint, or the like will prevent the zinc from sticking to that spot. Use a good degreaser after cleaning the parts to remove any last dirt and grime from them.

Finally you are now able to attach your part with the alligator clip and set it in the solution for plating. I suggest making some sort of jig to prevent the clip from entering the water - like a hangar - as you only want your part and the zinc plates in the solution. Also, it might be a good idea to run a junk piece of properly cleaned steel through first as it supposedly helps to pull out any impurities before you move on to your prized parts. Do runs in approximately 10 minute sessions, and between each one buff the plated portion of the part with some steel wool. As time goes on you may notice large crystals growing on the parts which is due to an excess of zinc in the solution. This isn't exactly bad, as generally they'll just fall off, but if you want to try reducing them I've seen some people add sugar to act as a crystal growth inhibitor. You'll probably want to do a few sessions (I did three per each section of the part that needed plating).

I hope that helps some. I can answer questions related to it and perhaps post some pictures of my 'janky' set up if anyone likes later today.

Awesome write up. Seems like a lot of effort getting zinc out of pennies but I may follow the rest!

Thanks! IMHO the pennies aren't that difficult, and if you're cheap like me (at least when 'cheap' doesn't cause problems), they're a great option :).

I had actually been in the midst of a supplement post when I got whisked away to do something quick, so here's that:


Okay, I wrote that last post very quickly so let me clarify a couple things.

- Plating occurs best on the surfaces facing the anodes. While the plate will develop on other areas, it may not be as thick - another reason why I did so many runs, enabling me to turn the part so that most sides got a fair shake.
- This process will produce, at the very least, some hydrogen and oxygen gas. I caution those who do this to not expose flames or sparks near the bath - anyone who has messed with HHO can attest to how combustible this mixture is... For the same reason, do not seal your bath while it is running or while the plates are still installed.
- As I haven't done the chromating step yet, I can't provide any results or helpful advice. Although from what I've read, it sounds like you just dip the part in a solution of yellow chromate - for a certain amount of time - and then let that cure for a day or so (light heat will quicken this process). I got the order status in today and it looks like the 'concentrate' will arrive next Tuesday, so prepare for a chromate update sometime after that.

So there's my little spiel. As I mentioned last time, questions and concerns are welcome.

Wheel weights are a good source of Zn. Just go to any tire shop they should have a bucket you can pick through. The Zn weights generally have Zn stamped on them; if not bring a magnet. The only other non-ferrous weight used is Pb, but that one will be easy to tell (cause lead is DENSE).

That'll give you pure Zn without copper residue.

Say, that's a great idea! Nice thinking :).

I would just like to put it out there that the method I detailed is not necessarily the best or only way to go about it. The aforementioned was really just some pointers and I'd encourage anyone who tries it to experiment a little (and of course report back their findings - although maybe a new thread would be better for that...?). Anyway, I hope it will give people a good starting point at the very least.

I suppose if you do a lot of parts, a $20 zinc bar might save you the effort of melting down a ton of pennies.

Wow, that's a hefty amount of zinc. You'd still have to make the bar into plates though - which may be interesting... Using a saw would waste a fair bit unless you collected all dust, which I guess you could melt down into a plate... intriguing... Good quantity idea though :).


Here'a another small update.

The top two thirds of the carb are now assembled. Floats have been selected (I decided to give one of my FB pairs another shot), installed, and adjusted to factory spec as a baseline. I took the secondary slow jets out of my spare SA carb as I knew they were a matching pair. I've also now plugged all holes that were on the list (other than the choke rod holes which I think I'll do after I can confirm a successful cold start - just for the sake of my sanity), and I also chose to remove the vent solenoid. Here's a few pictures of everything:
https://cimg7.ibsrv.net/gimg/www.rx7...4622606a19.jpg

https://cimg9.ibsrv.net/gimg/www.rx7...887f225af0.jpg

https://cimg1.ibsrv.net/gimg/www.rx7...d188094757.jpg

https://cimg2.ibsrv.net/gimg/www.rx7...7fe6724b03.jpg

https://cimg3.ibsrv.net/gimg/www.rx7...643ae10a07.jpg

Note the absence of screws in the last photo (since I'm going all out on cleaning, might as well electroplate them too.... ;)). The yellow chromate is still en route for Tuesday arrival.

Now I have begun working on the AP. I got some longer screws, but after making the new gaskets, I'm maxing out the throw (as in I can hear the metal cup not contacting the stops) with only one extra gasket on the reservoir side. However, the intake stroke isn't yet maxed out with again, only one gasket of the same size. I was reading through the boost prepping threads yesterday and noticed that there seems to be a 'long throw' AP diaphragm. I got the GP Sorensen kit (not the Hygrade mentioned in the threads) for both this and my previous rebuild without having read this info so.... is there a noticeable difference between diaphragms? Do note that I am using ~1mm gasket material. Related to the boost prepping threads, was the 1 & 1/8" separation between the holes on the AP arm extension from center to center, or between the nearest sides (I would assume center to center)?

Thanks for all the pointers so far.

You probably won't be able to save the shavings to create strips of zinc because the shavings will oxidize due to their high surface area and be rendered useless for what you are trying to do.

I bring this up because the venturis are a form of zinc with other metals alloyed together to give them resistance to moisture and oxidation, but they will oxidize too. Freshly cut ones are beautiful but will dull over time.

Galvanized steel lets the zinc layer be the sacrificial lamb, so to speak, to protect the much more reactive steel underneath.

To answer your specific question about the accel pump rod extension piece, I find it is best to aim for 1 1/8 to 1 1/4 and slot the holes for easy fine-tuning. you want a long travel accel pump diaphragm, which all the aftermarket kits should come with, and you need to add a little bit of preload on it at the idle position set by your throttle stop screw. Then you need it to finish its travel as your throttle is finished with its travel to 100% or wide-open. It takes some effort to "calibrate" the mechanicals of it, but it is worth getting right. Center to center, I guess is what you are wanting to know?

Another thing that is worth getting right regarding throttle position is to change the secondary opening timing from a stock 50% primary position where the secondaries begin to open, to something closer to 75% primary opening, which whips the secondary butterflies open faster and feels tons better on the GO pedal when you are using mechanical secondaries. It makes for a far better driving experience and has a more noticeable hard spot in the pedal compared to the weak stock hard spot. This hard spot provides better driver feedback during spirited maneuvers. This mod took me a whole month to get right so don't expect miracles over night if you decide to give it a try. It is good to have spare linkages on hand too... just in case you ruin your parts. It is a more advanced mod than the accel pump stuff you are working on now, but it is along the same idea of changing leverages and lengths, working ranges and stuff like that.

Cool, thanks for that info. I started messing around with the linkages last night and I discovered something interesting. I was in the process of of stealing some butterfly mounting screws from my SA parts carb when I noticed that the secondary throttle shaft on the SA is better designed for the 'cut half of it off' mod as the full sized portion of the shaft is smaller (I'll get some pictures up later this morning since I doubt that made much sense). With that mod - I probably won't trim the other side of the shaft or the primaries much if at all (it depends on how much they flex) - and the mechanical secondaries, I'm looking at building some alternative linkages and in the process, moving the secondary throttle stop to the near side of the shaft. I'm still working out the logistics of it, but it seems fairly straightforward and I've noticed a few threads mentioning that it would be helpful in reducing the tension in the secondary shaft while closed.

The other reason that I would be building a new throttle stop would be because the SA shaft doesn't have a provision for it on the far end. As such, if I do end up building this new throttle stop, it would have the extra benefit of providing a slimmed design on the visible side of the carb. Additionally, the SA secondary shaft is held in place with a c-clip, rather than a spacer between the end linkage for the vacuum box and the t-body on the FB's. This means that if everything goes well, I could remove the remaining vacuum secondary linkages allowing me to remove the throttle shaft from either side, which I suppose might come in handy under some circumstance... probably not though...

Note that the secondary shafts between the SA and FB carbs I'm using are identical (length, fittings, etc.) other than the SA's smaller uncut portion of the shaft, and it's lack of the throttle stop.

I don't believe in thinning throttle shafts to increase CFM.

As indeed I noticed in your boost prepping thread(s), and that is also one of the reasons I'm still debating doing it. To me it seems very similar to the booster centering arms, although perhaps the placement changes that fact. I find it curious that the secondary shaft has the dual sided shaft while the primary doesn't. I would suppose this is due to the greater forces on the shaft due to the larger throttle plates and quantity of air, however the primaries must also actuate things on the other side when the secondaries do not so... I'm up in the air on this one. I've seen both opinions on the subject, and having a relatively low supply of parts (only four carbs total, and I'd like to keep at least two operational at all times), not to mention the lack of a flow bench to actually quantify the results, I'm relying solely on the opinions/data of others.

If indeed it is not that much of a difference, I would prefer to not cut them, but if something can be gained I'd be willing to cut the reinforcement side of the secondary shaft and move the throttle stop. Speaking of which, here's what I was referring to on the SA vs FB secondary shafts:

https://cimg4.ibsrv.net/gimg/www.rx7...5c90cbf585.jpg


https://cimg7.ibsrv.net/gimg/www.rx7...3661775cba.jpg

The first photo is the SA shaft and the second is the FB shaft being held above the SA one. If you look closely you can see that the FB shaft has more material that ends up in the airstream. Perhaps if cutting is not worth the torque risk, swapping to the SA shaft would still yield some (albeit small) benefit?

Who all has done the trimmed shaft mods and what were your results (data for flow changes, noticeable shaft flex or lack thereof, etc.)?

Despite fedex's terrible tracking system, the yellow chromate did indeed arrive yesterday as it was supposed to. The instructions (which are conveniently printed on the front of the package) detail mixing one gallon of distilled water with 1 - 2 ounces of yellow chromate. I did three cups to one quarter of an ounce as my container was not that large (you want something you can both fit your part in, and keep sealed because you use practically none in the process). The 4 ounces I bought will probably last forever, so long as I don't spill it or let it evaporate. For reference, I got my yellow chromate from Caswell Plating - about 37 bucks, but it should last you longer than you'll probably ever need. After mixing the solution I dipped my part for about a minute, then shook/blew it off (to save any remaining chromate solution), finally leaving it to dry over night.

Anyway, it's time for some results. I've only done the one part so far (the dashpot bracket) but...

https://cimg3.ibsrv.net/gimg/www.rx7...98195b052f.jpg

https://cimg7.ibsrv.net/gimg/www.rx7...d98f3b1aa9.jpg

I'd say that came out pretty freaking good for a first attempt. That last picture shows how close the color is to the original plating found on the protected portion of the bi-metal spring bracket. Right now my biggest worry is the cable bracket, as getting into all those small creases every time (first to clean, and then after each round of zinc plating), is going to be a pain. I'm also looking at re-plating the screws so that I can use the stock ones that I removed the rust from without worrying about them rusting up again in the near future. To sum it up, if you're as picky as me about things being clean/new looking when you redo something, I would certainly suggest this as a great means of rust protection and overall enhancing the look of your carb that will be under your hood where very few will see it - it's still a good feeling even if you're the only one who'll know it's there ;).


Now for other carb stuff. I think I'm going to try cutting the SA secondary shaft. I did some more looking and it seems like enough people have had success with it (whether or not it actually helped flow I don't know), that it's worth a shot and won't be a guaranteed waste - and if it is, I do have a spare. Also, I'm still curious about the tapped airbleeds. When you go to tap them, I feel like you would drill out the original orifices. Is that correct, and if so, by how much? I've also got my carb fuel filter now as I have decided to remove the screens like y'all mentioned.

Recently I've been doing some looking through threads about the AP, and I'm beginning to think that I might somehow have the short-throw diaphragm. From the pictures that I've seen, the diaphragm I have more closely matches the 'old' diaphragms. The only photo I've found of what I believe would be the long-throw diaphragm shows one that has a smaller outer ring (as in a larger diameter gasket section) than the one I have. On the off chance that not all aftermarket kits come with the long-throw diaphragm, will I be looking at any major issues with that - even with the AP mods? With a maxed out throw, I'm seeing about 2.5mm worth of gasket between the carb body flange and the AP housing cover.

Very impressive. I do my own powder coating and now I'd like to try platting.

All aftermarket kits should come with the long throw diaphragms.

Nice job on the plating.

Thank you both regarding the plating results. It's been a bit of a mixed bag so far and I'm still refining my technique, and I actually did end up adding 100g of sugar to my solution as I was having a bit of an issue with large crystal growth, which is now reduced. I found out the hard way that you need to apply the chromate right after you've finished plating for best results (after some research too - I swear there's a forum for everything), which is why that first piece had to be dipped for a minute twenty. My second large part I did for the same amount of time - but right after I finished the plating - and it took up the color so fast I had to stop the process by rinsing it (which I never did on the dashpot bracket). Unfortunately it's become a deep yellow with little iridescence, but it is functional, so after I do some other parts I'll figure out if it's worth redoing to get a nicer finish.

Anyway, it's been a while so it's time for an update. Up until yesterday I haven't had much time to work on the carb but now I'm on crunch time (by my own choice) - the goal is to be done building over the next six days. Yesterday I removed the top portion of the secondary shaft (SA variant) and I am pleased to see that there is no notable flex. Something I hadn't notice though, is that the SA secondary shafts use the same size screws as the primaries for all years. While this may be ever so slightly better for flow, it worries me that much of the closing force is on such a small screw head - the FB's added larger screws and a throttle stop on the front of the carb. Regardless, I have successfully completed the most tedious part of the mechanical secondary conversion with no binding or potential spots for things to get hung up. I ended up cutting a new floating primary arm so that it could be longer (while also slightly adjusting the forced secondary closing angle so it wouldn't be hung up at idle), and after two revisions and a bunch of bending and other mods, I now have secondaries that fully open in only a 20 degree primary sweep (stock is closer to 40). This is darned near the maximum I think you can get without making a new, longer connecting rod for the primary to secondary arms. I also tuned the opening angles a bit as I noticed the throttle stops were allowing them to over-rotate a little. Now both the primaries and secondaries stop at straight up and down.

Today I'm going to continue plating, and also make a new secondary arm (the outermost one that attaches to the shaft). My reasoning for the new secondary arm is that I want to build a throttle stop on it, and add a second 'finger' on the other side of the freely rotating piece (the one people usually wire or weld together). I figure adding the second finger on the other side will allow easier disassembly, be sturdier than a wire tie, and avoid welding (which I don't have the equipment for). And as I already mentioned, I would be remaking it anyway to add the throttle stop so, might as well.

Concerns, suggestions, silence... all are welcome.

Plating looks great!,admit i haven't read thru your whole thread re the plating process,will do so now.