Carburetor Problem

[bstandley1]

While I was out for a drive today, my car started to run badly; it wouldn't idle and if I pressed the throttle lightly, it seemed like the car wasn't getting any fuel. However, if I put my foot into the throttle, the car accelerated smoothly. I limped home and checked for obvious things like disconnected vacuum hoses, but everything was intact. I also restarted the car a couple of hours later and the problem persists. BTW, the carburetor is a 600CFM Holley (1850 series), I'd appreciate any assistance in diagnosing the source of the problem.

Bob

[Naumoff]

Bob,
I would check the accelerator pump on the front bowl of the carb. Take the air cleaner off and, with the engine off, look in the Carburetor as you open the throttle and see if gas is being squirted into the engine from a nozzle at the top of the venturis.
If no gas then I would change the accelerator pump.
That's where I would start.

Tony

Unique 427 #4279480 427s/o Nascar toploader 3.31 Jag IRS

[Brent]

The idle issue would be seperate from the acc. pump. It sounds like a restriction in the idle circuit. Check the air bleeds on the top of the carb.(easiest first)

Does it run rich when it won't idle?





Brent
427 SC Chassis #4279401
Candy Apple Red/White
402 FE/Toploader/3.54

[JeepSnake]

I'm with Brent - sounds like you may have trash in the idle circuit. I've found the problem on Carter-type carbs by looking down the carb throat with the engine idling (take all appropriate safety precautions!) - if you see drops of fuel dribbling into the venturi or onto the throttle plate while idling, there's something gumming up an air bleed somewhere.

It still amazes me: you can take a brand new, 100% clean tank, add fresh fuel - even strain it through cheesecloth as you pour it in - and there will still be trash of some sort it in when you run it back out of the tank!!! (Noticed this on our new lawnmower last weekend!)

Good luck!

Zach Butterworth
Apple Mt. Cobra Pit Crew
(Mom & Dad's 427)

[TurnpikeBoy]

If it will run when off the idle circuits you've got the problem. That is, if it will take throttle and run at normal road speeds without issue then the idle circuits MAY be the problem. To be honest, this sounds like a vacuum leak.

I just replace the intake manifold gaskets on my car after the exact same problem; car would not idle but took throttle just fine, thank you. Found that the Fel-Pro Hi Perf gaskets were trashed (!), and a chunk even got sucked out of the gasket above the #6 cylinder, creating an nice air leak.

I have known several dinosaurs by first name, and have had my hands in engines of all sizes and kinds since Uncle Otto's first, but have NEVER seen intake gaskets that looked like these things. Mangled, twisted, warped - it is a miracle that there were no other leaks, including water.

Just an aside - sorry about that. If I ever learn how to post pictures I will post the ones I took of the gaskets. In the menatime, Holleys are easy to pop apart and use an jewelers eye loupe to scope out the passsageways in the metering blocks. A very fine piece of wire will help if you find something - and carb cleaner to blast out crap works good too. But look hard for vacuum leaks first; check carb base gaskets, missing caps and plugs, hoses off fittings, etc. This could save you some work.

Yeehah

[bstandley1]

Thanks for your help! Checked for the obvious ... accelerator pump is working fine, all vacuum hoses attached. Had my local small block expert take a quick look and he thinks the intake manifold gasket is leaking. He's going to do a pressure test on Monday to confirm. I'll keep you posted when the results roll in...

Bob

[bstandley1]

Found out today that the problem was in the idle circuit and the tech recommended I replace the carb. Thanks for the help ... and I'm relieved it wasn't the intake manifold.

Bob