Yea they dont like sitting dry. Hopefully thats all it is.

 

That's exactly what it was. I turned on the fuel pump today and the fuel level was perfectly centered in the window. Then I attemped to fire it up. Man, it fired up in like two seconds of cranking! The choke/fast idle rod/wire thing was adjusted perfectly and it idled on the choke at 1500 with a penny holding it out (no electric choke holder in this car). Actually, below 2k is what I've come to expect from Hitachis, and the engines always run fine like that. I guess RX-7s can get up to 3k or so, which I'd think is bad to do to a cold engine (with cold oil).

I let it warm up for half a minute while checking for leaks. I noticed the fuel level in the bowls was kinda low (remember the previous setup in this car was a Nikki and I haven't bothered to change the low pressure fuel pump yet). I got back in and took it for a spin. It runs better when cold than my REPU, but of course the truck is street ported and this engine isn't. Then I took out the penny and the idle was slightly choppy and high so I adjusted the fuel and air mxture screws until it would idle better. 900-1000 is usually ok for this engine, and this carb handled it just fine. It even revs and returns to idle very well. Not bad for just $10 on a set of 105 jets and an investment of time.

The next test will be to determine if the secondaries are opening. I couldn't actually feel them open because the primaries are so powerful. I went ahead and replaced the stock vacuum box spring with a shortened one. If that isn't enough, I'll remove the spring like I've done on my other Hitachis. It's ok to remove the spring from Hitachi carbs because the secondary linkage is different from the Nikki and the secondaries don't end up flapping in the breeze, but the linkage also doesn't lend itself easily to mech secs. It's a good compromise because they behave almost like mech secs (I can pop them open at 2k on one of my carbs).

I'm very happy with the results so far. I picked this carb up for free. It had a little water damage in the butterflies, it was covered in a nice oily sand mixture, and it looked hopeless to the PO. It's great what a little effort can get you. I'm no longer one carb short on my 13Bs.

 

Compressed air is your friend.

 

Yeah. I got an air compressor around summer last year. It's been a very good tool. I no longer fear 54mm nuts.

 

Can anyone tell me anything about these? SA? FB? Why Nikki changed them? Thanks.


The three came out of three different carbs. Left, 60, middle 70, right 90. Which should I use in my carb?

 

Keep them with the carbs they came out of. Work on your fuel jetting.

 

They all look like Nikkis from FBs.
You should experiment with #60 & #90 because they eliminate the variable that only #70 exhibits, which is initial fuel level setting. Besides, #60 & #70 orifices are close enough together to where the difference you would normally realize would be overshadowed by the fact that the #70 has a different level setting.
(Remember what I said about eliminating variables.)
#60 & #90 offer a wide enough range for you to gain an idea of what's going on in the carb @ Hi RPM. Anything in between and you'll need track time, a stopwatch, and an A/F meter to tell.

Hopefully others can chime in with some of their carb insight for you.

 

Carl, I now have a set of 91, 92, 93 and 94 to work with. I even used some _______ to clean the white corrosion out of them.

The 90 tubes are from an SA carb. The 60s are from an '84-'85 carb and the 70s are from an '81-'83 carb, I guess. All I know is that the '84-'85 carb has two nipples on top of the air horn.

Sterling, thanks for the advice. I very much appreciate it as this is something I can feel confident about messing with.

So if I understand correctly, #60 will give me a richer high RPM and #90 will be leaner? Then for low to mid RPM, the fuel jets take care of it. Lastly, I noticed one carb had different sized uh air bleed? I'll try to ge a picture later.

 

My '84-'85 and '79-'80 carbs have #150 and the '81-'83 carb had #170. Are these the air bleeds? Is there a quick and dirty way to make more power by going from one size to another?

By the way, what is the the one with 46 stamped on it? All three carbs have these with the same number.

 

O.k.
I'm done.
Jeff, it's time for you to pick up a book.

 

Jeff, dont mess with any of those bleeds. only the 4 main ones on the boosters. Work the fuel jets first, then tune in the hi rpms with the airbleeds.

 

Awesome Carl, thanks man! That's a very good answer. Besides, Paul Yaw's book isn't out yet.

How's this for irony: I had to put a fuel injection project ON HOLD for this carb stuff! If that doesn't make you want to retch, I don't know what will, LOL!

Sterling you're old and crochetty. You know, a great majority if your info I've used lately is two or three years old. Your posts from '02 are some of the best and I've been all over them like funk on pigs. Even though you'll probably not see this post (heh, yeah right), I sent you a PM the other day. I'd like an acknowledgement even if it's a big fat negative (just don't leave me hanging, please).

Now back to updating this thread with news of my continuing carb projects:

My Nikki had an accumulation of red-brown sediment. Both AP checkballs were stuck. A very small amount of white corrosion was present here and there. Nothing but a bunch of fun for me!

Through shear force of determination, I managed to free the checkball near the AP. Then I added some gaskets to the AP diaphram to add up to 1/8" (two on each side; they're sorta thick) and found some screws that are 1/8" longer than stock. I threw it all together with a slightly stretched spring and started manually pumping the AP lever with some carb cleaner sprayed into the bowl. It worked to free the other checkball. Now my AP system works. I also swapped in the banjo bolt that lacks the jet. I wonder if the pump shot will be too much now?

The next step is to figure out how to bend and adjust the lever extension...

Ok, I've installed a piece of steel strap that has holes every 5/8". With the rod on the 1 ¼" hole, I seem to get AP movement all through the primary circuit, but as soon as it hits the mechanical seconday linkage, the AP runs out and starts compressiong the spring. So what do you think?

 

The carb with the #70 air bleed and different emulsion tubes had 170 air bleeds. The other two carbs have similar emusion tubes and #150 air bleeds. The sets must work with each other, ne? Ok, that I can understand.

 

I finished the AP mod and I guess it's adjusted correctly. When the secondaries begin to open, the AP hasn't reached the end of its travel. It reaches the end about 5/8 or so into the primary linkage opening. When the secondaries are fully open, the long spring has compressed a little. Then when the throttle is fully closed, the vertical portion of the lever is parallel with the edges of the housing slot and the lever is just barely touching the AP pecker.

Having never, EVER worked on a Nikki before, let alone driven a car that had one, I don't know if the AP is adjusted correctly.

One question about the idle circuit. Is it possible to get red-brown sediment in the idle circuit so badly that the carb will not idle? Is there a way to check it without seperating the throttle body? Thanks.

 

Speaking of seperating the throttle body, er I'll get to that. Here is yet another water damaged carb. There are so many around here that I've lost count. It came off of a Pineapple Racing engine with nice ports and carbon apex seals. Let this be a lesson to never leave an engine out in the rain that has an air cleaner lid with a wingnut in the middle. I think this engine sat for like two years with water in it. Oh well.

I'm sure Carl will appreciate the port job on the manifold. What's it good for? Say, 5-9k or something? Pretty cool!

Since some of you still have small monitors and/or low resolution settings and would otherwise be forced to side-scroll, I'll only post the pictures as thumbnails. You can click on them if you want. They'll be at whichever resolution (size) that best shows the subject.

 

The airbleeds atop the emulsion tubes have been drilled and it has 155 and 170 fuel jets.

Notice one of the primary butterflies is open futher than the other? It's a good thing I had that '79-'80 carb sitting around. I hope to have this carb back together and on an engine very soon.

 

I finished swapping throttle bodies on that Pineapple Racing carb yesterday. It's trying to be a Sterling carb, but isn't quite there. I think the AP spring was stretched or replaced because it feels stronger than what I've messed with so far on my FB carbs. I didn't open it on this PR carb for fear of breaking or damaging the gasket, and the check ***** both worked fine anyway. The AP diaphram 'pecker' is all the way out touching the housing, and the AP lever needed to be adjusted to account for this (not quite vertical). Otherwise, I bet it gets a bog since it's got mech secs and really, really hogged out venturis. The mech secs are also a little different to wire than an FB carb due to a change in the linkage. The secondary butterflies are little stiff so I gave the linkage a little WD-40 and it seemed to help. Not too shabby considering these carbs were both water damaged to the point of nonfunctionality. Now I have one good carb and one totally dead carb.

I've noticed AP squirters have one, two or three dots on the top in a little circle. Do the dots tell you what size the squirter holes are? To my eyes, the three dot style has the largest holes (like that tells you anything). The Pineapple carb has two dots and no jet in the banjo bolt (infact, the bolt's hole looks a little bigger than stock and the two upper holes also look bigger). My '84-'85 carb has three dots and I replaced the jetted banjo bolt with an unjetted one from a '79-'80. I can't remember which carb had the one dot squirter.

 

nice job on the mani do you have bfore and after pics?

 

I didn't actually do the manifold. It's a '79-'80 manifold and I do have a stocker kicking around. I'll take a few more pics today. This should get interesting.

 

i think this was covered somewhere not sure if here or another thread but to me that mani looks like a single plane mani which i thought was bad for our cars... maybe that ridge in the center is good enough... I think sterling talked about it somewhere.

 

Carl is the person who's into manifold porting. Yeah, it looks like a dual plane, or a semi-dual plane.

 

awesome definately interested in hearing how that runs. Hey have you thought about matching the cabr spaced to the mani? I thought about doing a dual plane type of thing to the carb spacer with a stock intake just to see what it does.

 

I've thought about it, but I don't want to risk ruining the spacer or the manifold. Speaking of which, I think one of these manifolds was ruined by a dumb kid and a dremel tool years ago. I've never tried it, but according to Carl, it won't flow right since it's been ported incorrectly. It's the 2nd one starting from the left. The 1st is a '73, 3rd is a '79-'80 and 4th is '81-'85. I guess I could try porting the '73 to match the Pineapple manifold, or at least to match the '79-'80's dual plane (only much less ugly).

 

It appears FB and Hitachi carbs share a common pedal travel. That means I can throw a Nikki where my Hitachi currently is and it will all work out. Well, the choke cables are different, but at least the butterflies should open 100%. Hmm, I think the OMP rod might be troublesome.

 

No it won't.
Think about it...The rod could have a "Z" bend in it to make it exactly the same radii at the sgaft as the the other carb...if they're nat already the same.
Worry about it to the point of making sure it works, but it should be fairly easy to figure out compared to some of the other things you've done so far.

BTW, your expertise is needed in this thread...
https://www.rx7club.com/showthread.p...=1#post3781880