Technical Carb question

I have an Edelbrock AVS2 on a mild SBC 350 in my roadster, 300 rear gearing with TH350. This carb runs perfectly all day long with zero issues...until...I go WO throttle. When WO no issues all the way thru the power band, but when I let off the throttle back to a cruising speed in burbles and sputters, like its flooding and will continue to do this at all speeds no matter how far I drive it and will now die at idle...starts back up easily, let off throttle and it will die...if I shut it down for 3 or 4 hrs all is back to normal again and will run great, until I stab the throttle hard, then rinse and repeat...there are no lags or flat spots at any time, but a WO blast of ANY length 5ft to 500ft and the issue returns.

I called Edelbrock and they were stumped....I suspected maybe one of the metering rods may be sticking open or the secondary air plate may be sticking open, as it feels like its flooding, but I have checked and everything is free. I also installed an edelbrock carb spacer, thinking it may be a hot condition...

Has anyone had this issue.....thx Ron

 

I would look at the distributor

 

Make sure your float level is set correctly. Lower it a little.

 

fuel pressure?

 

Had this happen to me, the Fuel pump kept pushing too much pressure after high demand, internal pressure spring and parts corroded and sticking. Bought a new pump

 

yeah may be......its a mechanical pump but im gonna get a pressure regulator to see if that helps

 

Yeah, fuel pump for me too.
No need to be more than 5psi at idle.

You'll need BOTH a regulator AND a pressure gauge.

Mike

 

Update....installed a quality pressure gauge and has 11.5 psi to carb....this is most likely the problem...pressure regulator ordered, should be here in day or two. thanks to all who chimed in.

Since the car does not vapor lock, regardless how hot it gets in central Calif, should I use a bypass style regulator or will a non-bypass type do the job?

 

I like the bypass, it helps keep the fuel the correct temp. I think they regulate better.








Bones

 

I made my own bypass line Tee'd into the carb inlet with an .080" restricted line returning to the filler neck in the tank of my 460 powered '46 pickup.

 

It depends on the pump. If it's the Carter style, then no, they can be run without a bypass vary easily, and without problems.
I've run the carters on a coupla cars, many years without problem or failure, without a return. And I live in the 100° + in the summer, SoCal.
Matter of fact, I have a 12 volt Carter, (big gold motor can), run by a 6 volt "positive" ground, pushing fuel to a single barrel carburetor, no return. The regulator is turned down to 3.5psi !
Again, been on there for years, no problems !

If you have the Holley blue style pump...then yeah, it might be better to run a return.

Mike

 

Update....got the regulator installed and set at 5.5 psi......all is good....starts, runs, idles better.....

 

What concerns me is the folks at Edelbrock didn’t offer that advice. Glad you got it fixed though.

 

Nice fix. Yea , those Edelbrock carbs hate high fuel pressure. 5-5.5 is good to go.

 

Ron Brown , heads up with fan mounted as it is without a shroud , you're only cooling about 1/2 your radiator . Also , by mounting it with those " thru core" mounts ,you're risking damaging the radiator , just a little unsolicited advice ..