Idle drop and bogging down GT40

[setty2706]

Ok.... I am stumped

I hope you can follow how this played out because it doesn't make sense to me. My 82 has a GT40 motor. 600 Holley carb ford motorsports dual plane intake. The car has never given me one hesitation or any issues in the last six months. It all started on Easter sunday I was cruising around and my idle jumped up to 1100 RPMS so I thought maybe I hit the choke arm when reinstalling my dual snorkel air cleaner. I pulled into a buddies and flipped the butterfly on the choke and had no further issues that day. I took it out the other night to take my daughter to her mothers and it acted like it wanted to die as I took off from a stop sign. I drove a few blocks and when pulling into her driveway I pushed in the clutch and the idle dropped below 700 and died. The car started right back up without issue and drove fine about 3 miles and it started acting boggy and could hear it popping through the mufflers. I got the car back home and removed the hair cleaner and it appeared to be running fine with a 800-900 RPM idle. NOW THIS IS WHERE IT GOT ODD TO ME. I reinstalled the air cleaner base (no lid or filter) and I could hear the idle drop down a little bit. I let it sit and idle with only the base on and when I tried to lay the lid back on the engine died. After a few cuss words I started it back up with the air cleaner on and it started perfect and the idle was correct..

I went out tonight after work and drove it around the block with no starting or idle issues. It appears to be happening once its at operating temperature.

Any suggestions and info would be greatly appreciated

I was hoping to see the rain hold off for Saturdays cruise but now I am just hoping the ole 82 can make it

[mustang_gt88]

I say can the Holley and go edelbrock. I had nothing but bad luck with Holley. Even some of the same issues on a gt40 motor with a Holley on it.

[setty2706]

I have a edelbrock 600 ..may throw it on before Saturday

[setty2706]

You coming out Saturday Jeff?

[slow86fiveoh]

I ran nothing but a basic holley 600 dp with the choke horn machined off with gt40 heads, single plane intake and f cam for 4 years and it always ran flawless.

[setty2706]

I never had any issues until this ..just has me stumped.

[mustang_gt88]

Yes I will be there sunday

[Stangman]

Dumb question.... is your carburetor tightened down? perhaps its come loose a little and creating a vacuum leak at the carb base gasket/intake?

[setty2706]

Thats a great question....because it doesn't happen until its warmed up..(heat expansion)

[Stangman]

It sounds like a vacuum leak to me. Could be intake gaskets as well.

[setty2706]

Iam leaning toward vacuum leak...just cause it doesn't due it all the time just randomly decided to act up... Plugs look good...

[Stangman]

When's the last time the carb was gone through?

[setty2706]

Really not sure on this carb....I can't figure out if its the carb why would it run..start and idle perfect 90% of the time then suddenly act up...PVC valve is good..no damage or dry rotting on vacuum lines ..all lines hooked up...iam going to carb clean it after work tonight and check for idle surge ..(carb gasket and intake check)

[timdsellers]

I had something similar on my old cj7. Turns out some goop from inside the gastank got past the filter and partially clogged the fitting going into the carb and would run fine at times and other times not so much. Figured it out as soon as I got frustrated enough to take off the carburetor and rebuild it.