Hey guys, Just kinda thinking ahead and was wondering if anyone is running a Quadrajet on a single plane and if so how well does it work? I was planning on getting a quadrajet from QuadrajetPower this summer since I'm still having issues with my spreadbore (unless I get it squared away) but after I build my engine I plan on going to an SP3 and would like to use whatever carb I have already invested in. Or would I be better with just a new Holley this summer? Thanks, Ryan
It should be ok but when you floor it you only have the front squirters to rely on whereas a Holley dbl pump will have squirters on both ends. If you are a person that does not race I would just stick with the TA Stage 1. The SP3 is meant for a Holley but that is just my 2c. I don't think Chevy or Ford guys use a Q-Jet with a open plenum intake like the SP3. I really do not think the 455 guys run that way either. DP intake Q-Jet would work good, run open plenum I think it should be a square bore carb, double pumper preferably.
It's got a mean part throttle lean stumble that I just cannot figure out. To the point of just using the throttle under normal driving (right about 1/4 throttle maybe less) it jumps to 16-16.5 ish on the afr gauge and if I stab it it just backfires, afr gauge pegs lean and dies. Caught fire one time too from a nasty backfire. I'm sure if I had the time I could figure it out and as it warms up a bit I might be able to figure it out but pretty frustrated with where it is now.
Timing is 12 for base, vacuum is off of manifold and has lightest springs so its all in by 2400 I believe. I think is around 34* total mechanical but would have to double check. I have checked for vacuum leaks before and couldn't find any but can double check that as well. But it seems to fine otherwise, cruising afr is right around 13 and wide open is rich at 10.5-11 so I will be getting that down. Have played with all sorts of squirter combos and seems to do better with bigger but not good. If I roll past that point on the throttle then I can mash it just fine.
Try 14 to 16, check to see if the nylon limit bushing is still in the distributor, if not install it and up the initial timing. pump cam tuning may be in order as well, at what rpm roughly is this happening? TQ converter ? Rear gear ratio? All these things come into play when working out throttle transition issues. Can seem daunting but you'll learn alot from conquering it
Stock Converter, 3.08 gears Will try upping initial and will check on the bushing Don't have a tachometer but can hook up my multimeter temporarily which has a tach function Does it in park as well not just under load
play the lotto. those are better odds happening than trying to make a q/jet work on the s/p. I started using a s/p years ago. q/jet or t/quad is not for performance. visualize the venturi's exit. 2 little holes and 2 big holes and a big space in the middle. little flow in the front, big flow in the back and no flow in the big space in the middle. it is way out of wack. the 350 s/p will love the d/p. oh and don't forget the rev limiter. the 350 rpm will climb fast. its been 12 yrs since I started on the 350 project. using the d/p, a s/p and now a 4-71 s/charger, all the setups have run a 650 d/p. none of it makes any sense, especially on the s/c. should be using 800-1000 cfm. engine is in love with that 650. go figure. 9.2 @ 145....more to come
3600lb, 3.08 , and stock tight converter is going to make a mechanical secondary carb tricky but not impossible. but with it doing it in park, I'm leaning towards idle circuit transition and the timing, have u worked with the idle mixture?, ignore what the afr gauge is telling you, adjust for max vac then work with base timing and idle mix till you get it to "rip" nice and clean from idle. Make sure you only use as much throttle angle as needed, try to get your idle from timing and idle mix, it can load up while low rpm cruising then when roll into it , it has to clear it's throat so to speak.
Everytime I do anything on the carb I go back and adjust for max vacuum on the mixture screws. I have pulled the carb off and set it so the transition slot if squared but I was wondering about how much the secondaries should be cracked open or should I go back and shut them? Right now they are at a hair cracked open trying to help with it idling so rich. It idles at 10.5 when adjusted for vacuum, but I can also screw the mixture screws all the way and it doesn't die. I'm assuming I need to close the secondaries completely?
Just my 2cents worth. I run A Quadrajet with open plenum intake on the 455 in the convertible. Mostly street, some track. Performs perfect. And we build a significant amount of Quadrajets for open plenum intakes and race cars, where performance matters. I don’t see a concern for running it on any engine, especially the Buick 350!
Let me answer that for him, yes it is a sbb 350 he runs and he was able to setup a roots blower because he is an awesome machinist and did everything himself custom.
Had that cough and spit once with a out of box Holley. 50cc frt. pump and 37 shooters cured all. Brown pump cams. Are you running a spacer? You will have no stumble at all once you dial it in.
I tried with my SP3 to run my Q-Jet, it worked ok, except when slamming the throttle wide open, the engine didn't like that I gave in and bought an AED 850 DP... Holley style Double Pumper. BIG DIFFERENCE! As others have said, the Q-Jets lack of a pump shot on the secondary side it lets the engine go lean when suddenly slamming the throttle wide open.
I am running a 1" phenolic spacer, I have switched my 50cc pump to the front with the brown cam and still same results, and I believe I have 37s front and rear currently.
The Quadrajet has pull over enrichment for the secondary shot. It can be modified for performance. Some of our units are on 650+ hp engines running 9’s. The Quadrajet has no issue being on an open plenum intake.
Sounds like if someone wanted to run a quadrajet on a single plane you guys can make that happen but by merely just taking one that you already have it won't be optimized for such an application. So if I got one (probably a stage 2) for my car this summer could I send it back to you guys to mod for when I build the engine and put the single plane on?
