Quadrajet question

[napa68]

I have a new car I am working on and trying to improve it's cold start / transition performance. The car (71 455 HO Pontiac) will start right away, but it is really rich! The choke and choke pull off is operating just as it should. It will not take any sort of throttle as it gets really rich.

What I did notice is that it appears to have fuel coming out of the primary air bleeds when you try to blip the throttle (and it stumbles). I have not noticed that on any other quadrajets before. Is it a sign of the float being too high? When it's warm, runs great. Plugs look good, and oil does not smell like there is any sort of fuel dilution. Admittedly, I have not checked engine timing. This is a relatively fresh engine build (1500 miles) and about 2 years old.

I am told Cliff Riggles did the carb and built it to the engine specs.

Am I on to something? I just feel it should run much better in cold transition.

Thanks for your consideration,
Tim

[tjs44]

Give Cliff a call or email.He can also be reached on the PY site.Tom

[olredalert]

----My 69 SJ GP had similar problems and I sent the carb to Eric. Couldn't be any better now going on 4/5 years.....Bill S

[Lynn]

Could be as simple as a sunk float. Sometimes those floats get saturated and start to sink. Instead of solid brass floats, they are nitrophyl. However, if Cliff recently went through it, this isn't likely. Still possible, just not likely.

The other possibility is the fuel pump. Get a fuel pressure gauge and plumb it inline. Start it up. I would not be surprised if it is 10 - 12 psi. Should be 4 - 6. For some reason, almost ALL of the manufacturers of the new mechanical fuel pumps are using a spring that is TOO STRONG!!! I guess they though if some is good, more is better. That spring determines pressure. Over 7 psi, and most needle and seat valves are just overwhelmed.

Some guys use a needle and seat with a smaller diameter seat. The smaller surface area means it can withstand more pressure before being overwhelmed. I DON'T like this approach, especially on a big cube motor, as that now smaller seat diameter also restricts fuel, and you may starve the engine during a long full throttle run. I have a couple cars I just gave up on mechanical pumps and went to a low pressure electric pump. Kind of a pain, but it is getting really hard to find a good mechanical pump.

[WILMASBOYL78]

----My 69 SJ GP had similar problems and I sent the carb to Eric. Couldn't be any better now going on 4/5 years.....Bill S

X2

-wilma