QFT 650cfm on 351W Stroker

[Austria_Cobra]

Hi there!

I have a SPF Cobra, bought from Hillbanks, and had a Pro-System Carb 834cfm on the 427cui Stroker (from Automotive Engine Specialties). The Carb worked fine over 2500U/min, below it was not working fine. Also the missing choke is a problem for me. OK, some adjustments and with a warm engine it could be fine, but I would not be satisfied.
So, I changed the Carb to a new QFT with e-choke and mech. Sek. Don't think about it again

The engine is hanging realy fine on the throttle, runs smoother and not as loud? as before. I am definitely faster on the road. But a bit less power on top, but that was precalculated.

First Setup:
Prim: 72; Sek: 82; Idle: 70, main: 28
Gas in the middle of the glas, 6,5psi regulator, floater and needle OK, fuel vent installed, power valve is 45 (4,5), choke works fine, double pumps are adjusted (not nozzle and valve).

Some things are still to improve, like the exorbit waste of gas
I use an AFR Tool to measure and at Idle if have a rate about 12 . Much too rich. Should have 14,3-14,7(= 1 as perfect mixture). Idleneedle 1 turn out.
Driving is between low 11 and 12. Power or getting off the gas is up to 14.
So my setup is much to rich, but the jets should be OK... ?
Under 2000U/min the engine bocks around and isn't nice to run, this will be a couse of the rich mixture I think. If I increase the idle up to 1800U/min this gets much better but not a solution.

So where could be the problem situated?

THX and regards from Austria!

[Austria_Cobra]

no PVC on the carb, on the manifold port a power break

at 800U/min the manifold preasure is about 8inHG, at 1200U/min 12inHG

[Gaz64]

650 is not big enough for your engine.

I would have fitted a QFT Q-750.

[Ron61]

I have an 850 Double Pumper on my 351 stroked to 418 and it has been on there since 1997. Works great and was built by a racing shop in Los Angles. No choke and it does run rich at low RPM but a few seconds of higher RPM and the pipes are a perfect gray. Everything in my engine was built to match what I have on it so that may be why it works so well.

Ron

[Austria_Cobra]

Hi guys
don't worry about the 650
in the US size matters - I know

I had that carb on stock and it works fine, especially in low rpms.
Don't need of full power, I don't care about the last 10%
and I know to reduce the rev.
Just want to have a smooth run.

[Mohuska]

I have dual Quickfuel 650's on my BB 547 and the engine was very rich at idle and low speed.

My QFT's have 4 idle circuits per carb...so you need to shut off the rear two (or at least down to barely any fuel) for your carb. This resulted in a perfect idle and low speed performance..(with a little adjustment of the idle air).

Keep us posted on how it is going.

By the way....where in Austria are you?

Mike

[RET_COP]

jets seem a step or two on the rich side for a 650. Try a 70P/78S, you'll know when it's going lean, it will start surging. Go up 2 from there. Set the floats 25% in the sight glass

I agree with others a 650cfm is small for a stick shift light car with 350ci never mind a 427ci. That Pro-System 834cfm carb was a gem.

I have a 780 Pro-system no choke. In 5 minutes or so [depending on weather] its warm and ready. A cold engine should never be driven anyway. Always take the time and properly warm a performance engine before driving.

I don't understand some of your numerical terminology.