DreamInRotary

iTrader: (49)

You guys totally reminded me of this


Pretty crazy that you guys all found out the same thing in different way!

I want nothing to do with carbs personally, I just suck at them. Growing up in the technology age makes me much more partial to EFI setups with wiring and ECU's.

peejay

Jeff - I ain't gonna itemize any kind of response I will allow that you've done way more with Nikkis than I ever have and doing things, and learning from them, and applying that knowledge, is the way forward.

I will point out something very important/basic about venturis that often gets overlooked... The intake manifold shape is very close to one port/one venturi. This means the airflow is heavily pulsed. A small venturi may have higher overall velocity but if it is causing too much of a momentary pressure drop at the start of airflow, then the air never gets moving. You can have venturis that are too small for good low end

And I have a turbocar now... if you know Mitsubishi turbo sizing then you'd understand what a "12T" would be... small by tiny! And it's dual scroll to boot. It gives a four cylinder engine the linear power of a mid sized V6 while getting the fuel economy of a large V6

Jeff20B

iTrader: (13)

j9fd3s, yeah at some point Sterling discovered that you have to keep the cast iron base plate within the generation or year range of the carb. 78-79 is different from 80, 81 and 82 are the same, 83 is a little different and 84-85 are the same. Some of the FB carb parts can swap around without issues but I'd think mixing SA and FB parts would cause problems.

I wonder if Sterling managed to mix them up? I think he did because when you read his website, he seems to think the 1978 - 1981 Nikkis all had separate air and fuel idle adjustment screws, which is simply incorrect. The 78-80 carbs had two idle screws while the 81-85 only had one. It's therefore quite possible most of his bum carbs were due to his tearing several down in lots, cleaning each lot and then reassembling with whatever parts were nearby. After enough complaints he finally started keeping the parts separated and contained within the right years. In other words towards the end of his carb building business, he most likely got it right. Too late for some, it would seem.

I think my carbs have the little bit of miss at part throttle too, can't really remember. They also have the brap under decel. I kinda like it; reminds me of my REPU Hitachi days. The dashpots also get removed.

Wow so a Sterling wasn't all that powerful? I thought they were the bee's knees if you see what kentetsu and a few others have to say about them (but then what are they comparing to? Stock?)). Sounds like my hogged nikkis would walk all over a Sterling.

So since Sterling stuck to his 22mm venturis, I guess he really was right at the textbook perfect size. I guess we can't fault him for that. His carbs still don't sound very impressive powerwise though. Not that I'm recommending against them or anything. I'm just saying there is a bigger world out there once you start modding your own carbs.

As for the mechanical secondary mod, I finally figured out what was inherently wrong with it, and why Sterling did the accel pump mod the way he did. It is due to the secondary slow air bleeds #1 and #2 letting in too much air and causing the bog when you force the secondaries open against their will. In other words before the carb's conditions are right for them. Think about what I said in the previous posts about how they "shape" when and where the vacuum secondaries open, and how they cause the extremely long secondary delay when you boost a Nikki. The NA carb only ever had a very short "hiccup" before the mechanical secondaries came online, and Sterling did what he did to "fix it". He didn't really succeed the proper way, it seems. The accel pump mod was kind of his brainchild that he was proud of as it was something not even Mr Yaw came up with. He sort of copied the way Holley did it.

I think I have a fix for it. I've never actually tried this but my Nikki tuning sense is telling me that if you were to fill the slow air bleeds with solder but leave the main air bleeds alone, you would eliminate the hiccup and not need to do the accel pump mod. Because if it reduced the 1 to 2 second painfully long delay in boost down to a half second or less, it most certainly would completely eliminate the short hiccup in an NA carb. No further mods needed other than basic tuning like you said.

Jeff20B

iTrader: (13)

I remember my first time messing with a weber on PercentSevenC's engine. Yep I was affraid of it messing the engine up too. He stuck with it though and managed to get it street tuned without a wideband. That's pretty hard core. Then he got a wideband and started tuning for boost.

My first wideband was tested in the GLC briefly. I didn't undestant what the numbers meant. So Percent went and ehad started tuning my Hitachi's idle. He didn't give th eengien what it wanted. Instead he aimed for some specific number on a wideband that I don't remember. The end result was that it did idle, but only while warm.

My next wideband experience was on the turbo in the brown car. Fortunately by then you had a chance to learn to give it what it wants and mentioned it on the forum. I used that knowledge to not pay attention to the wideband while idle tuning but noticed a pattern developing. Across all four boost prepped Nikkis I tested, the engine would idle best at 12.2. So when I'd change a primary fuel jet or some air bleed or something, I started aiming for 12.2, in a way breaking the "rule" about give it what it wants, but in the end because it really did idle best at 12.2, it made setting up the idle circuit on another carb a much faster easier experience.

Speaking of comparing tuning times of a carb vs EFI, as I would discover new and better ways to get the hardware to do what I wanted it to do, I'd then implement it on all the other carbs, saving probably tens to hundreds of man hours. Kinda like sharing a base map with someone who has a similar setup. Of course every engine is different.

I only ever tried to get the carbs about 80% there. The final 20% to be performed on the actual engine the carb was intended for. That's why I added an O2 bung to the MG's header last week. I can only get it so far in the brown car on a 74 ported engine compared to the mild streetport in the MG.

Jeff20B

iTrader: (13)

DreamInRotary, I got into rotaries back when the FC was still new and I always considered EFI to be a thing of the newer cars, and never something I was interested in. I got into rotaries to do a few specific things:

•get a rotary truck
•streetport the engine
•throw in a Racing Beat Holley and one of their intake manifolds
•upgrade igniton from points to electronic
•build a "free flow" exhaust system

I did accomplish most of those goals only to discover what I wanted was based on the REPU my friend had, and that my ideas were influenced by him. So I decided to branch out and learn all I could about rotaries and how to get them to do what I wanted. The orignal goals turned out to be let's say less than ideal for a truck. If I needed a faster vehicle that would perform the way I wanted it to, a 1st gen was the better choice. So I decided to set up the REPU in a slightly different way:

•dump the street port and dump the stock non nitrided 3B irons for a set of nitrided R5 irons ported to 74 spec to retain more low end torque.
•dump the stock 30 pound flywheel for a 26 pound GSL-SE or better yet an S4 NA 24 pound and use S4 NA rotors for better low end grunt
•I tired the RB Holley and it wasn't as nice as I was hoping so I decided to throw in one of my hogged Nikkis
•instead of just a "free flow" exhaust, whatever that means, I searched and researched and studied and figured out a better long primary solution which was quieter and had more low end torque than I was expecting, while still free flowing plenty at high RPM
•instead of just upgrading from points to electronic, I also went direct fire

This turned out to be the perfect solution. I even tried a Camden 5" with an Edelbrock which felt like the truck had a V8 in it. Not too shabby! However the Camdens tend to be power limited to about 150 to 160HP max and parasitic at low RPM when they're not boosting so I swapped it out in favor of a hogged out boost prepped Nikki for a turbo swap. It currently has an NA tune until the turbo goes in. Still lots of other work to do to the fuel system, wiring, tubular exhaust manifold etc. Just waiting for better weather.

And speaking of finding the same things out in a different way, Robert at RS and I found out that a turbo tune wants leaner jets than an NA tune. We are the only peope to have ever said this. I mentioned this somewhere buried in the long post above so decided to say it again because it's important. Everyone else on the forum including bad83 (as a convenient example) say you have to use bigger jets on the secondaries while I found out you gotta use smaller jets. He said to use #200 mikuni jets which I'm pretty sure are the same size as 200 jets you can buy from Mazdatrix. The stock Nikki size is 160. I found that I had to use 150 jets which might actually still be too big now that I've blocked off the slow air bleeds and made the main air bleeds smaller than stock. I might need 145s but don't have any right now. Oh well, the engine is safe with the 150s if just a touch too rich.

I have a quick question about the stock EFI T2 engine swap in an FB you did recently. In the video it shows a side by side comparison of the stock 12A vs the T2 swap and how they differ in acceleration. While you were driving the T2, does it ever just break them loose on dry road? I'm not asking with any ulterior motives trying to suggest my custom carbed turbo setup is better and that it's what everyone should be doing. Far from it; I'd just like to see more boosted Nikkis on the forum like there used to be because now I can contribute!

I've seen videos from the 2nd gen section where people post what their T2s can do and they just accelerate like any "normal" EFI car. Very little real excitment. Pretty boring actually. You can watch the boost gauge go up and that's about it. Is that how your T2 transplant behaved? Or was it "fun" as j9fd3s said about his carb experiences? And by fun I mean fun, not scary or a handful or any other somewhat negative adjectives.

I guess the real reason I'm asking is because of the stark differences my friend's 84 GSL with the S4 NA swap had compared to my NA hogged Nikki which then later got a turbo. Even while NA mine was "better" than his and "more fun" in every way. The turbo is in a whole other league so kinda hard to compare to a stock NA 6 port. I just honestly thought the S4 NA setup would have more in it, you know? I knew they weren't fast, but in a lighter FB chassis I was really expecting more. Plus my brother had a stock GSL-SE which wasn't as fast on the freeway compared to my friend's REPU which could accelerate from a roll like the GSL-SE was standind still. Just curious what your stock T2 swap was like.

j9fd3s

iTrader: (3)

i do that too, 12.2 is a good starting point, if i'm using a wideband. the Tr3 was positive ground, so couldn't use the WB! and since those carbs only have a lean/rich screw that does the whole fuel map (like an old 1 **** AFC), i just leaned it out a couple flats, and went for a drive, couple more flats went for a drive, until it stopped getting faster, and then i went a tad richer. unfortunately i did this in the summer, so in the winter it wasn't happy... if you can tune in winter its best.

that is great example of what i'm trying to say, you would think that turbo = more air = more fuel = bigger jets, but it doesn't seem to be true. my P port was like that too for some reason, Mazda has a jetting chart, and for some reason mine ended up being much different than the chart.

the hardest part though was to ignore the piece of paper, and just pay attention to how the engine is actually running!

that is the thing, i had two to look at, and the old one was very nicely done, and then the new one was pretty slapdash. it didn't help that it didn't work either

Jeff20B

iTrader: (13)

peejay, glad you responded.

What you say about venturis and the nature of the rotary engine makes sense. It's gotta be why the bigger you make the venturis, the more low end power you get. This is exactly opposite what Sterling and Carl have always said. And I think you nailed the reasons why. There is only so much you can learn from a flow bench, it would seem.

So nowadays we should approach it this way: Sterling and Carl meant well, and their findings with a flow bench made sense, and the end result was better than stock for the most part (which could be argued either way), but now that the truth has come out, we need to stop the hero worship and learn how to mod our own carbs. They can be modded to be much more powerful than a Sterling and much more fun than any EFI swap could ever be, and FAR easier if you have a few basic tools and some skill using them.

I used a die grinder to remove the bulk of material from the venturis. Then a dremel for final clean up and shaping. I grabbed a handful of washers of various diameters, stuck a nut and bolt on them to poke in the venturis to use as ID finders and would "hog out" the venturis until the washer would go to the same depth or position in each venturi. This is to keep the sizes equal (as close as you can by hand). I'd maintain the venturi shape as much as I could and I think I did an ok job. No need for a lathe, unless you have one. Up next you have to cut the booster support arms by hand and use a set of small files to shape the other side into an airfoil shape. Sterling often complained that he still had to do this part by hand. Yes it is tedious and time consuming but worth it. And I still like Sterling's accel pump mod for the obvious increase in duration, but it reduces the volume so the nozzle and banjo bolt can be drilled but I disagree with the size of holes he'd drill in the nozzle. I'm willing to try a stock nozzle now that I know about filling the secondary slow air bleeds with solder to eliminate the secondary bog, and I now know how to machine the heads of the secondary main air bleeds to accept fuel jets or holley air bleeds of whatever size is needed (typically smaller than stock 140). The primary air bleeds usually don't need to be changed as 70 is a pretty good size for an FB carb. But do swap the nickel plated 60s from the secondary side over to the primary after you drill them out with a .045" drill but. This is needed to calibrate the idle circuit for bigger venturis and fuel jets that aren't over sized. Remember Sterling barely touched on this and Carl didn't know about it at all. Or if he did, it was classified as one of the "secrets" that goes into a Sterling carb. Carl said if you don't cut the venturis right, no amount of jet and air bleed tuning will "correct" the air fuel curve. I disagree. I've found that the nickel plated 60, drilled to .045" and swapped into the primary side, corrected the curve and fixed any idle issues. Then the stock brass primary slow air bleeds get filled with solder and swapped into the secondary side. It's deceptively simple to make a hogged Nikki work if you know about this.

Ah, glad you finally got into turbos. Aren't they fun? It's like driving through a thicker atmosphere without all the wind resistance.

peejay

I never once had a "secondary bog" but I also never went to mechanical secondaries, I would just remove the spring and let intake flow open the secondaries. It's close enough to being the same except, apparently, there's enough of a damping effect remaining that it prevents a bog. I never felt that the throttle response wasn't good enough so there wasn't ever a need for more.

My turbo car? You literally wouldn't know it was turbocharged unless you looked under the hood carefully. No wheezing noises, no whistling noises, no drill noises, no lag, no boost gauge. Tiny turbo, high compression, low boost, and a transmission that kicks down if you breathe too hard and in that .5-1 second to shift the turbo has spooled up already. Looking at a scantool it runs up 1-2psi boost just mildly accelerating on the highway.

The other car, on the other hand, is old school no-compression heavy turbo probably measure lag with a calendar stuff. Should be a riot

My OTHER other other car, I can't decide if I want to put a Weber 32/36 D-whatever progressive carb on it for old-school vibe, or a pair of Dell'Orto DHLAs on it for the old-school vibe...

Jeff20B

iTrader: (13)

j9fd3s, I noticed the same thing with Hitachis. You'd have to tune for summer and tune again for winter. Just a little turn of the air and fuel screws was all it took.

Percent tried to use the standard available jetting chart for his weber but eventually had to abandon it too.

Sterling was obviously under some tight deadlines and his quality suffered. He also mentally went off the deep end toward the end there. I only hogged out 5 or 6 carbs last year over 6 weeks and it took quite a toll on me. Granted it was the first time for me which makes things more difficult than for a seasoned veteran, but I could feel myself mentally slipping. I had to finish up the last carb and take a good long break.

People on the forum started asking if I could do their carbs and I had to turn them down. It's tough work when you don't have a lathe. Then of course you still have to test drive them to make sure everything was done right. Sterling eventually stopped even test firing them and I think it shows with all the bum carbs he sold.

He once complained he hadn't even driven his car in a really long time. Well that's nobody's fault but his own. He could have made time. It's a first gen for crying out loud. It should have been driven that whole time and enjoyed with an occasional carb swap or two. I mean carbs were his side business, right? The least he could do... It's like the waterbed salesman who sleeps on a regular coil spring mattress. Would you eat food prepared by a skinny chef?

Heck I got to the point of doing several carb swaps per day while I was doing some hard core test and tune in October last year, not to mention the total number of times both NA and turbo tuned carbs were swapped in and out over the whole year. I think I had at least 100 carb installs and removals just in the last two weeks of October. If I were to add it all up that would be four carbs times four installs and four removals times several months or 4x4x30x3=1440 where 30 is the number of days and 3 is the number of months (even though it was actually more like 8 or 9 months total), but I don't think it was that many. What was Sterling's excuse? lol

I wonder how hot under the collar Sterling and Carl will be when they eventually come back to the forum and read this thread. I'm not trying to "diss" or at least that wasn't my intention. I just needed to get it out there. I had no idea peejay and j9fd3s both had access to bum Sterling carbs. I've never even seen one in real life. I've only ever seen and very briefly driven one Yaw carb around a parking lot for a minute or two. It was alright but nothing special. Just ok.

If Carl or Sterling feel threatened by anything I've said, it means they took it that way intentionally as needing to feel like a victim that day for whatever reason. If their work really was as good as they claimed, they wouldn't need to come here and defend it as it would be good enough to stand on its own. Again not my intention to diss them or their work, but to inform people of my findings and realizations from my own experiences. I keep using Sterling and Carl as punching bags because they were so visible and exposed on the forum back in this forum's greatest time of growth and usership (usership?). This is also back when turbos took a back seat to Camden when they were gaining popularity before the truth came out about them too.

We all made mistakes in the past and hopefully learned from them. I think I did. That's probably why I'm still here, because I'm still learning. I didn't dig into my first Nikki until late 2004 so I'm something of a new comer to them. Well maybe not so much anymore, but at least I know how to tune them now to keep a turbo engine alive. And that was all I ever wanted, to avoid the whole EFI monster.

I've come full circle on things like ignition (DLIDFIS), porting (74 spec), carbs (Nikki), forced induction (turbos), or NA exhaust (long primary), clutch/flywheel (light steel) and now recently added starters (NA FC nose with a 2kw motor). Also recently added learning how to read a wideband (AEM UEGO), swapping in an EFI rated fuel pump (MSD 2225) and a boost referenced fpr (Mallory 4309). Nothing else matters. This is it, really, for me.

Just goes to show you may think you have all the answers but the reality is there is still more to learn out there. My next tasks are to test all of the above in one or two more vehicles to see if lightning will strike twice or three times (I didn't say thrice because it sounds too much like "the rice", which I'm not into).

Jeff20B

iTrader: (13)

I used to remove the spring from Hitachis all the time and it worked great.

Others have said they thought you couldn't simply remove the spring from a Nikki becasue it would just flap in the breeze. I didn't know the diaphram was sturdy enough.

But thinking about it just now, I know why it's ok to remove the spring from a Nikki and that it will work. Why? Because of the offset of the shaft on the secondary throttle blades. They are pulled closed by engine vacuum through leverage. So any time it's idling, the secondaries are kept closed. Then I think the diaphram is still stiff enough at higher throttle openings where vacuum is reduced, to keep them closed, or the leverage is still enough. Then at some preset point controlled by the secondary slow air bleeds and the cross drilled hole from the primary circuit to secondary diaphram actuator nipple, the secondaries are opened and all is well. Does that explanation make sense?

Sounds like you have some fun projects over there, both turbo and NA. Have fun!

peejay

You're waaaaaaay overthinking it. Or underthinking it.

There's a mechanical interlock that keeps the secondaries from opening unless the primaries are open. All vacuum secondary carbs will have this.

Jeff20B

iTrader: (13)

Oh right, the spring loaded linkage. Duh me.

Inspector71

Remember, I haven't owned an Rx7 since 2009 and just getting back in. As far as the Nikki carb goes, were they and are they still made in Japan? Didn't the gen 1 Rx7's come with a 4-barrel? I went on the Nikki site and only found 2 bbl carbs.

j9fd3s

iTrader: (3)

the were made in Japan, it is a 4 barrel. since the last carberetted Rx7 rolled off the assembly line in 1985, it wouldn't surprise me if Nikki doesn't make a 4 barrel carb anymore

t_g_farrell

iTrader: (1)

I did my Nikki on a whim. I saw that an FB was at Pull-A-Part and wandered down there to look
at it. Saw the nikki and thought, that would be fun, lets pull it for $50 and see what happens.
Best fun I've had with my car in years. The Dellorto is great but I was tired of no low end torque
and some issues on right hand turns that I had to drive thru. Don't get me wrong, the carb was
excellent and will probably go on another project but I wanted better.

I did the Fat Nikki thing over a long period of time (2 years), so I didnt' get burned out on it.
I had my own issues as Jeff well knows. I would just leave it and come back to it at sometime
later usually to discover I did something stoopid and once it was fixed moved on.

I now can change the jets on a nikki without removing it from the intake or the car. Just pop
the top, use a handy sideways racheting flathead driver, pop out the old jets, put in the
new and bobs your uncle. In fact I'm thinking of swapping in some fatter jets on the primaries
again but I want to get an AFR setup installed first to make sure I get it just right.

rotaryjunkee

Wow, what a long, interesting and imformational thread.
Makes me want to take my plans on going efi turbo and scrap them.
Pull out my yaw carb and maybe with some of you guys help, go nikki turbo.
Would definitely be cheaper, haltech or microtech ecu is not a cheap part of the build to purchase

Sent from my samsung gs4 using RX7Club app

Jeff20B

iTrader: (13)

I'd definitely go Nikki turbo. Especially on a Yaw. Any mods he did will compliment a turbo tune if you just do a few easy mods in steps like I mentioned.

If you have any questions, start a new boosted Yaw thread and I'd be more than happy to help.

Hey guys, here's a feeler type question. Should I scrap my current plans on having a Camden in the GLC and just go Nikki turbo?

S5 turbo, 3" DP that contracts down to 2.5" under the car where it joins the current 2.5" center section. Semi-locked dizzy, MSD fuel pump, Mallory 4309.

From having test driven the Camden in this car, it just doesn't wow me. I've tried several different setups in here ranging from a stock ported 20B with a MegaSquirt that wasn't tuned (was too much engine for the car, took years to set up, ultimately wasn't worth it) to a couple of 4 port 13Bs with hitachis and eventually an RB Holley 600. The Holley was the only carb that ever wowed me. But being a Holley, had its share of issues that a Nikki doesn't have.

I've tested this same Holley in the brown car and it wowed me in there too, and it also had the usual carb glitches etc. Then I tested a hogged Nikki set up for NA and was really wowed! So assuming the GLC is going to be similar, I can't not do this swap!

I have never tried a weber in here and I have zero plans of ever doing so. The only other common rotary carb which I've never tried here is the Nikki. It's not that hard to do an NA Nikki test. Maybe once the weather is better.

Now that I have some experience tuning a Nikki for boost, I'd like to streamline everything to just running Nikkis and either NA or boost depending on the vehicle.

I think the GLC would do well with a small turbo like an S5. If it goes in the GLC, it will get a custom tubular manifold. The car never got a long primary so I also wouldn't have to fab a whole complete new exhaust. Just connect the 3" DP to the current 2.5" center section with a little reducer piece.

I was this close (--) to doing a long primary this time last year but never pulled the tigger. It's as if the rotary gods were stopping me for some reason. Now I can see why.

This car has had EFI in it before, so the fuel system is relatively already there. It just will need an MSD fuel pump and a mallory 4309. It has a 3/8" send that will get repurposed into a return, and a new 5/16" hardline will get bent up and installed alongside the existing 3/8" as the new send, according to Mallory's instructions.

And now the final piece is the engine. It is a 4 port 13B with old school MAZDA font housings that have really tiny exhaust ports. I'm thinking I'll swap these out for either a streetported 12A, so it drives the turbo better, or a different set of R5 housings ported to T2 spec (to drive the turbo even better!).

Or another idea that is kind of off the wall, is to use some FD irons, FC rotor housings (with diffusers removed of course), and an R5 rotating assembly. I have all these parts. The only problem is it will need an intake manifold for a Nikki. Well, I have one, but it won't fit an FD intake port or bolt pattern. I'd need to make an adaptor plate. Fair enough. I have some tools around here. It will space the intake further out by only about 3/4" or so. If it's getting a custom exhaust manifold anyway, the turbo will be located up and forward so the air filter occupies the battery area. Obviously the battery will get relocated.

The nice thing about FD irons is they are light, plentiful and handle boost better than any other generation. I can get another set of FD irons without too much difficulty. It's the rotor housings and rotating assemblies that are a little harder to come by.

Of course the current orange and silver engine already exists and won't need all the extra engineering. It can be seen here with a holley being test fitted on a stock manifold. https://www.rx7club.com/old-school-o.../#post11270597

Thoughts?

rotaryjunkee

Ok sounds like a plan.
I need to finish welding up my turbo manifold to run my 91 t2 turbo then oil and coolant lines.
Any thoughts on changing my fuel pump setup?
I have a carter external tank fuel pump, was thinking of welding on a sump tray and weld on some an fittings to an external inline pump and filter. To larger fuel lines and then to an rrfpr ending up at the nikki

Sent from my samsung gs4 using RX7Club app

Jeff20B

iTrader: (13)

Um, get a boost referenced fpr, not a rising rate.

I just added some rubber standoffs to my fuel pump today. It needed a little noise isolation. Also connected up the return line and should be able to connect the send line from the fuel pump to the hardline under the car tomorrow. Then maybe get the mallory in.

Your Carter doesn't have enough pressure "headroom" for boost. I was told to install an MSD fuel pump and a Mallory boost referenced fpr. This combo, even with the wrong size fuel send and return hardlines under my car, was able to get down to 2psi which if fine because the Nikki wants 2.5 psi in vacuum, but sometimes would ride at 3psi which did seem to bother it. Then in boost, the boost referenced line connected from the carb hat to the boost referenced nipple on the mallory, tells it when to up the pressure to match the boost in a 1:1 ratio, not a rising rate which is different and not recommended on our setups.

I've just been working on getting my fuel hardlines hooked up according to mallory's inctructions where you have a 5/16" send and a 3/8" return. I am using a GSL-SE tank so my return is only 5/16", but it probably won't be a problem as long as most of the hardline under the car is 3/8".

Speaking of which, I have a story about PercentSevenC's setup that you may find interesting. His car was an 83 so it had a 5/16" send and a 1/4" return. We didn't know about going to a 3/8" return when we set it up, so we only upped the return to 5/16", which then contracts down to 1/4" right up where it goes back into the tank. This turned out to be ok as his setup could be adjusted all the way down to 1psi.

I'm curious to find out how low mine can go once I'm done redoing my hardlines.