[RARON455]

Hopefully I can get some advice on where to start with this, I have a 69 bird with a 9.75.1 comp. 462 solid roller with a worked 750 holley, mechanical secondaries I have the floats set correctly, the idle screws are in 1 1/2 turns, it has a 6.5 power valve in the front only. Ported Iron heads, I am feeding the fuel with a mallory 140 fuel pump, I have the Holley regulator set at 6.5 psi. The problem I am having is this, when I floor the car it pulls fine, but when I let off the car rpms drop and it wants to stall, and If I come to a stop it will die, It is flooding, but I am not sure what else to check I would greatly appreciate any advice on this. I dont know if this could cause it but there is a hose on the top of my gas tank that was plugged off, maybe a vent? When I drive the car and stop to get gas (92-93 octane)I pull the cap off the tank and there is a ton of pressure that blows out the neck, Should I be using a vented gas cap? maybe a carburetor problem?
Thanks for any help..

[Tom Vaught]

You need to fix that vent hose asap, there should be no pressure build-up in the tank if you have the right sized vent hose and it is open.

Not a carb problem. A venting problem causing a carb problem.

Tom V.

[tikiklubracing]

Put a whistle vent in the back bowl.

BG makes them in 1 1/2" and 2" long.

OR

Run a piece of hose between the vents and cut a hole on the upper part of the bend.

You probably have slosh.

[BruceWilkie]

When I was young and dumb I inadvertantly blocked the vent to my tank(thinking that disabling my emission controls was going to give me better performance). Later that week I took a 200 mile trip. When I went to fill the car with gas it took a pair of channel locks to remove the cap. It had actually started to collapse the tank. When the cap came loose their was a woosh then a bang. Next day had a puddle of gas under the car, the tank had cracked! That was an expensive lesson.(I do remember getting better than usual mileage though!) Fix that vent!

[BruceWilkie]

Actually your idle mix screws might be out to far!(Causing rich/stalling condition) I've had a few Holleys out of the box that needed slightly less than 1/2 turn out from seated. You could have debris in your inlet needle/seats (or defective/worn), or you could try lowering fuel pressure. Had a defective gauge once showing lower pressure than actual cause flooding.

[RARON455]

Thanks for the advice I appreciate it, I'll drop the tank and open the vent. On the carb I have a piece of hose on each of the vent tubes, they are put together on the air cleaner stud. Is there a trick to adjusting the IDLE air screws? I have heard of using a vacuum gauge? I am not too sure of the best way to adjust them.
Once again any advice will be greatly appreciated.
Thanks
Ronnie

[lust4speed]

What model of Holley 750? A club member has an 850 Avenger carb that is driving us up the wall stalling on moderately fast stops. Have done the normal fixes with no help - even purchased Holley's vent tube for 4x4's that looks really trick but didn't solve the problem. Have been told that all Avengers have a weakness for flooding out on a stop because of the design of the secondary power circuit. I didn't believe them, but I'm running out of alternative reasons for the problem.