General Category > Quadrajet Carb Talk and Tips

How much hp can a quadrajet support?

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WESTOF7:
I want to build a stock appearing(to the average person) n/a 400 sbc based off a dart block with ported afr heads I'm going for as much power I can get out of it and still stay streetable. I'd really like to keep a quadrajet on it and an hei maybe with an aftermarket box. The cars a 86 z28 with full suspension coilovers completely stripped r spec bfgs built t56 and a ford 9 inch baer 6 pistons all around. Its built more for open road track and autocross but will be making alot of trips down the 1/4. Can a quadrajet be made to work? I know the guys in s/s run pretty fast with these but havent been able to find any information on their setups. 

omaha:
   That is a very good question and one that I have not heard yet!  (at least not that I can remember).
I will take a guess. If you could get a true 800 cfm, at 400 cubic inches I would guess 600 HP would be feasible.
Would probably require alot of rpms (7000?) aluminum rods, ultra light pistons/pins / serious crankshaft.
That 400 rod stroke ratio is not the best,  but of you have a tall block....maybe 600+ (just a guess here).
I am not knowledgable of the Q-jets  functioning at high rpm or what modifications would be needed. I know those ss racers can be pretty secretive about stuff. (and sneaky!)

Cliff Ruggles:
One of our customers uses a later model large cfm unit at 750hp.  His car runs high 9's in the 1/4 mile at 136mph.  He has at his disposal a Quick Fuel 1000cfm Holley, it runs no faster anyplace than the q-jet.

We have a Super Stock customer running mid-9's with a small block Chevy using a smaller "750" cfm unit, built from an early 1970's Chevy divorced choke truck carb.

My own engine uses a 1977 Pontiac carb, it makes close to 600hp, and powers my daily driven 73 Ventura to low 11's at over 120mph.....Cliff

WESTOF7:
guess I was on to something when I started collecting these after all and all my friends thought I was crazy  ;D . Do you do any additional work to the higher hp cars that you wouldnt do in a normal performance rebuild? Like porting anything like that? Any problems from running the fuel bowl dry if I held it to the floor?

omaha:
Yes, I think "keeping the fuel bowl full" is a majpr factor for a HP Q-jet application. Just concentrate on fuel delivery. Design a system from the start.
       There are some "porting" things that can be done. Just obvious minor stuff like casting flash smoothing, throttle shaft trimming (careful here...), matching up the top/main/base etc. Another mod involves removing the  outer ring (in the primary bore). Not sure if this mod is right for everyone. Maybe on a "race only" deal. 
    I always wondered about removing the  "bump" in the large bore primaries. Have never tried it but maybe will experiment with that............GOOD LUCK!!

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