[dv657172]

Car ran fine at track a month ago.
Started it up today and wouldn't hold idle at 1,000 rpm for any extended period of time. Would run for a short bit then fall down and die.
Fuel pressure guage shows 7.5 lbs even up to when car stalls out.
Car appears to run fine at 1,000 rpm and higher, just as it has in the past.
May have run fuel down a bit low at last track outing but have added 5 gallons of new fuel since.
To start the car I also have to pump accelerator while cranking, even when hot, which I have never had to do in the past. Car has always been easy to start when warm.
Carb is a Holley 750 DP.
Sound like a carb issue? What should I check? Haven't worked on a Holley before but have books/manuals on them.

[25stevem]

The first thing to do once the motor has run for ten seconds is to turn it off and see where the fuel level is showing in both of the fuel bowl site plugs if you have clear ones, if not then remove each plug and if the carb is getting enough fuel it will just dribble out a little.
If no dribble and seeing that your car was ok a month ago then you can rule out the floats being off.

My next best guess then is that the idle air bleeds on the top side of each throttle bore now have Cato in them and are clogged.
Get some carb spray and a the metal section out of a bread tie rap, or a wire shard and run it down into each air bleed to brake up and flush out the blockage .

Also once the motor has run for a few seconds how does the accelerator pump work, with the engine off do you get a nice shot of fuel down into each primary bore?

[dv657172]

Thks for the ideas Steve, will look into them tomorrow

[TinInjun]

Also make sure the accelerator pumps are actually putting out fuel. The check valve under the squirters have a tendency to stick over time and need to be removed and cleaned if they sit. Your fuel pressure is too high. Needs to be no higher than 6 psi.

[25stevem]

While the above is true, it will not make for a engine failing to restart when fully warmed up.

[dv657172]

Float settings seem ok - a little to no dribble
Cleaned idle air bleed holes out w/paper clip and carb cleaner
Accelerator pump appears to work fine, 2 strong shots of fuel
No change in condition

Recap:
Car difficult to start even if warm, have to pump pedal
Will idle good for a handful of seconds at 1,000 rpm then it falls down and stalls out (warm or cold)
Holley DP is carb

Also checked fuel filter between tank and electric pump and looked like new. Car also has a mechanical pump

[DOC]

Vacuum leak would be my guess

[dv657172]

Definitely not a vacuum leak as I threw on a friends Demon 850 and while the borrowed carb needs a rebuild and adjustment the car started right up and idled strong at 2500 (unable to adjust carb enough to bring it down).

Any thoughts on what carb issue could be?

[Dragncar]

Rebuild your carb and go from there.

[Tom Vaught]

Originally Posted by dv657172

Definitely not a vacuum leak as I threw on a friends Demon 850 and while the borrowed carb needs a rebuild and adjustment the car started right up and idled strong at 2500 (unable to adjust carb enough to bring it down).

Any thoughts on what carb issue could be?

Apples to Oranges to me.

If one carb is tested at 2500 rpm and will not adjust to a lower idle speed it is a poor comparison.
I have had race Dominators that would idle at less than 1000 rpm when set up properly for 20 minutes under no load.

Your buddies carb needed a rebuild and adjustment for sure.

Tom V.

[dv657172]

Tom

My friends Demon carb was used just to confirm that the issue is with my Holley.

Since it ran fine although at an elevated idle, the question is what may be the issue with the Holley that it cant hold an idle at 1,000 rpm for more than a few seconds without stalling out.

Thanks
DV

[Tom Vaught]

Sorry sir, but 2500 rpm is not a elevated idle. Not by a long shot.
Cars go down the road at 70 mph on the highway at lower rpm.

Tom V.