New holley dies at idle after warmup

[Mr. Trans Am]

My 750 holley idles fine until you drive for a few miles then in gear at a light, it will idle fine for a few seconds then stumble down. Starting is somewhat hard after and it will repeat. Sometimes giving it a little gas will help but it still may die. What should I be looking at? Is this vapor lock? Should I look to a insulator type carb spacer to keep carb temp down? Any help will be appericated.

Oh, stock 440 cam, new chain 4deg. advanced, 383 mag 102,000 miles, auto, new stock hi stall, edelbrock duel plane. electric choke carb. mag exhaust manifolds.

[Mr. Trans Am]

Also new MP electronic kit, converted to elec. voltage reg. 69 RR was old mechanical regulator and points.

[pishta]

check your float level. I bet the fuel level is creeping up and out due to a bad seat or leaking O-ring. Of course you need plastic bowl plugs to monitor this. It is worth looking at.

[Mr. Trans Am]

I thought float level was set at the factory, right? Should it be changed according to the engine? I have had the bowl off several times to find the right jets. The one in it were way to big for the 383. Could I have unsettled something in changin them.

[rumblefish360]

I doubt you unsettled it by taking it apart. Check your choke setting, float level and fuel pressure. When you changed jets, are you sure you adjusted the idle screws. Somewhere in the area of 2 1/2 -3 turns out is were it sould sit.
Keep on tinkering with it. You'll get it.

[Mr. Trans Am]

i'll be looking t some of this stuff tommorrow. car has sit at friends body shop for many months since i even looked at it. keep the ideas flowing, i see a pattern to what is being said though.

[Mr. Trans Am]

I'm pretty sure I set the idle w/ a vac gauge like I always do, screws should be about right, not a bad call though.

[rumblefish360]

Thanks for the comp. Lets see...The car sat for a few months? Change the gas. Was there any varnish build up since you had it apart? Also , How well did it come apart? Possible gasket material in the jet? Looks clean looking down the bbl's right.
The floats were set at the factory. They might have to be adjusted if your running a lot of HP. They could have been knocked out of wack too. Otherwise, it should be fine. Those plastic plugs pishta was typing about. I bet there the clear units sold. There good to have. Makes life easy.

[Hammer 74]

I had the same problem years ago with my holley and I found it to be dirt in the fuel holding the needle and seat open. Only at idle would it be noticable. Stumble,stumble, couch, die. Hard to start because it was flooded. Wait a few minutes and it would start. Installed a good fuel filter , a mallory with replaceable element and had on more problems. good luck.

[Mr. Trans Am]

Did the same thing the day I drove it out there, so this is not new, car wasn't driven before any of this. For sure had new fuel filter but will change again just cause can't hurt. Has those reuseable gaskets so nothing came off.

[kingjr]

I would check the float levels as well. What jets are you running now? What is your fuel pressure? Make sure the air bleeds are clear, maybe they got plugged up at the body shop?

[Mr. Trans Am]

I doubt the carb has stuff in it from the body shop because it sat out under a cover all the time and was only in a booth w/ no dust when I worked onb the windows. Wasn't uncovered unless I did it. Good thinking though.

ok, I checked the mix screws and they were at 2 turns each, so I went w/ 2 1/2. Seemed to help but I didn't drive it around, it has no tags or insurance so it's a risky operation like the trip home was.
Didn't get to hook up vac gauge again on it, ran out of time.

Didn't checked float level yet. Busy didn't want to fool w/ that now. Had trouble putting pressure gauge on and that took up my time.

Couldn't get my fuel pressure gauge on it as the T it is on was to big to plumb in. Have to do some thinkin on that one.

Was ordering stuff for my rear end project on Challenger and went ahead and got a 1' spacer to try. That might let me run my duel feed fuel line like it was designed and in that ccase it has an opening w/ threads to properly attach the pressure gauge. As it sits, I can only run the setup upside down. It hits the distributor if installed correctly. Hopefully that will improve my situation.

Thanks again for the replies and I hope others will comment if they see anything I missed.

[pishta]

see if you can get a vacuum guage on it somewhere and plumb it into the cab. Maybe you are getting a vacuum leak at warm up?