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Q-jet build

2K views 10 replies 8 participants last post by  MouseFink 
#1 ·
Alright guys you convinced me to build my 1971 qjet! It's going on a 1984 454 mainly stock with headers and a holley street dominator intake. I have the qjet apart right now and need to know what I should order to make this motor come alive like for example should I need a hi flow needle and seat or would that make a difference on a stock motor? Thanks
 
#5 ·
Alright guys you convinced me to build my 1971 qjet! It's going on a 1984 454 mainly stock with headers and a holley street dominator intake. I have the qjet apart right now and need to know what I should order to make this motor come alive like for example should I need a hi flow needle and seat or would that make a difference on a stock motor? Thanks
Never had a fuel starvation problem on a stock motor of any kind because of a stock needle and seat being too small.There are different sizes of seats though.
I think Cliff Ruggles book says the largest stock one is .110 inch.
Proper fuel pressure would be an important factor too.
My P 389 with a q jet has a .110 and it never hungers. It is a mild street build.
 
#7 ·
I have always preferred to use a Rochester Q-jet since 1967. In 1969, I traded the Q-jet from my 1967 Pontiac Firebird 400 for a 1966 Pontiac tri-power, hoping for more power at WOT. There was not a dimes worth of difference, in fact, the Q-jet seemed to make more power on demand with the air valve secondary and had better fuel economy when using the small primaries.

I have a 1962 Chevrolet Bel Air 2-door sedan with a 327 CI / 300 HP engine and 4-speed. From the experience after is switched the Q-jet with a tri-power on my 1967 Firebird, I decided to replace the 1962 Carter AFB and intake manifold on my '62 Chevy with a 1968 Q-jet and intake manifold. I installed a rebuilt 1968 Rochester Q-jet I purchased at a local parts store and bolted it on and made a new fuel line from the pump to the carburator. My '62 Chevy immediately gained more performance and fuel economy with the Q-jet. The Q-jets are hard to beat for a high performance street engine with 800 CFM on demand air-valve secondaries.
 
#9 ·
I would buy Cliff Ruggles quadrajet book, and then give him a call with your carb number to find out what level of rebuild kit he recommends. The book is not organized well to provide directions for a simple stock rebuild, since performance tweaks are mixed in with stock rebuild info, but it has a lot of extremely good information.

I rebuilt mine as stock, with a few minor tweaks/fixes, and have never gone back to try any of the performance mods. However, I'm running it on one of the GM 350/240hp crate engines, so its basically a stock engine.

Bruce
 
#11 · (Edited)
On my 1967 Firebird 400 Q-jet, I snipped off the little tab on the air valve secondary lock-out with a pair of dikes. That little tab only allowed the air valve to open 70% at WOT. I know GM did that to the Q-jets used on engines used in the 1967 Pontiac Firebird 400 in order to lower the HP to weight ratio for insurance purposes. That immediately raises the 325 HP of that engine to 335 HP at WOT. As far as I know, the Q-jet iused on the 1967 Pontiac Firebird 400 325 HP engine was the only Q-jet that had a secondary air valve stop. I have looked at several different 1966 -1969 GM Q-jets and no others had the air-valve stop. If GM had used the Rochester Q-jet without the secondary air-valve stop on the 1967 Firebird 400, that vehicle would be in the same insurance category as a 1967 Corvette!

The Q-jet used on a 1967 Pontiac GTO 400 CI / 335 HP engine did not have a air-valve stop. The engines in the 1967 Firebird 400 CI / 325 HP engines and the 1967 GTO 400 CI / 335 HP engines used same 068 camshaft and the same 670 heads, but the 1967 GTO hardtop was 370 lb. heavier with 10 additional HP.
 
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