Hi everyone:

I'm having a problem with gas fumes in the car at part throttle operation and when I nail the throttle and wind up to about 4000 RPM and then back off. Full WOT (red-lining) between gears (5000-5500 RPM) or slow normal driving does not give me the smell, only seems to be when I partially get on it. I'm running the following:

- 350 CI Chevy standard bore flat top pistons

- 492 Fuelie heads w/2.02 intake 1.06 exhaust valves - 67cc combustion chambers for about 10.25 compression ratio. The heads have been mildly ported and cleaned up on the intake side and have had a 3-angle valve job.

- "472" factory GM aluminum '69 Z28 intake high-rise manifold

- Holley 670 CFM Street Avenger carburetor w/elect. choke

- MSD Billet "ready-to-run" electronic distributor w/MSD Blaster 2 coil - set to 12 degrees initial timing and 34 degrees total timing all in by 3500 RPM

- Crane Hydralic cam #967601 - 350 HP corvette cam, 447-447 lift, 222 degrees @ .050. The cam was degreed and installed 2 degrees advanced for better low end performance.

- Double Roller Timing Chain and Gears

- 3:73 Posi rear-end w/Muncie M-20 trans w/2:52 1st gear, the engine is seeing enough gears to get the RPMs up quickly

The car starts great cold and runs very strong with no stumbling, detonation, or spark knock. It pulls hard through 6000 RPMs. The only problems are a hard start hot and the fuel smell that comes in the car at partial throttle operation. The hard starting occurs anytime after the car has been running (hot) and sits anywhere from about 10 minutes to 2 hours (until the choke reactivates). It takes several seconds of "rapid" cranking for the engine to catch, and sometimes the gas pedal must be floored to get it to start (as if clearing a flooded engine). It almost seems like it is trying to fire, but isn't (the starter is really cranking fast, as opposed to when it cranks over cold or if cranking with the coil wire removed). If it sits for only a few minutes, then it will pop right off on a "bump" of the starter.

Could either of these 2 problems be caused by having the cam 2 degrees advanced thus allowing the valves to open too soon and dumping too much fuel into the combustion chamber that isn't getting used up? Is it possible I'm flooding the engine partially during part throttle operation and/or when the starter is rapidly cranking before it cathes enough to run? Any suggestions you can provide me to correct one or both problems will be greatly appreciated.

Thank-you for your time, and I apologize for the length of this post.

Thanks,

Camaro350

It sounds like you're "boiling" the fuel in the float bowls. You might want to try a Phenolic spacer under the carb. (not plastic and not aluminum).1 inch works best but 1/2 inch is fine. You have a choice of open or 4hole styles. 4 hole seems best for the street. Good luck. http://hometown.aol.com/zz430droptop67rs/

fuel leavel could be too high or the pump could be too high,you only need 6-8 psi of fuel pressure.you may want to change the gaskets on the metering block of the carb,if they're old ond brittle they leak,even if the carb is bran new,i bought a new holley 750 and the gaskets were hard as a rock,had to change them no problems after that. also your power valve could be in gauging to soon causing the fuel smell at part throttle. hope i idin't bore you,good luck!!!

fuel leavel could be too high or the pump could be too high,you only need 6-8 psi of fuel pressure.you may want to change the gaskets on the metering block of the carb,if they're old ond brittle they leak,even if the carb is bran new,i bought a new holley 750 and the gaskets were hard as a rock,had to change them no problems after that. also your power valve could be in gauging to soon causing the fuel smell at part throttle. hope i idin't bore you,good luck!!!

Thank-you everyone for the suggestions.

I forgot to mention in my original post that I am currently running the open plenum carb gasket. Could that be the problem? Should I use the "4-hole" gasket and/or spacer?

I am also wondering, how would I check/adjust my fuel pressure? I do know that the pump pumps really well, as I had one heck of a time stopping the gas from coming out when I did my rebuild, every little turn of the engine was causing gas to spurt out.

Yes, the carb is a brand new street avenger. Is it still possible the metering block gaskets could need to be replaced? Is there any way to tell if they are bad w/o pulling the carb and pulling both bowls off?

Thank-you again for all the suggestions, I think I will try the 4-hole gasket on the weekend.

Oops, forgot to mention/ask, how can I tell if my power valve is coming on too soon? Is there any way to adjust it if it is?

Thanks again.

Regards,
Camaro350

[This message has been edited by camaro350 (edited 05-23-2001).]

have you tried to adjust the fuel level yet? the four hole gasket will do pretty much nothing.

sldhd:

Yes, I have adjusted the fuel level in both bowls so that it is just at the very bottom of the sight glass. Is there some way to adjust the power valve? I do know my back fuel level was high from the factory, however now it has been staying where I set it, at the bottom of the sight window.

Thanks for the suggestions,

Camaro350