I have a Holley 570 new carb on an air gap manifold that I can not get to idle below 1000. Runs a short time then dies. Checked and found that when I sprayed starting fluid around the carb when I got to the front of the carb the engine smoothed out and raised rpm. Okay, took the carb off and replaced the 2 gaskets with 2 new ones. (Holley) These had the metal plate that is used to mount the throttle and TV cable. Same problem. The base of the carb and manifold both look flat. The carb base does however have the circular milling marks but very faint. Since I can't get in touch with Holley for a couple of days I have a QUESTION? Is there any kind of non-hardening, fuel proof gookum pucksy that I can use on the gasket surfaces to see if I can stop the leak? Thank you for any assistance, Fourdy
try Seal All. It is a contact adhesive and sealant. I have used it to seal a leaking gas tank. About any hardware store will have it. I don't believe it is non-hardening though. I would think it can be removed from hard surfaces fairly easily.
Are you sure you have the correct gasket for the manifold? A friend had a problem like that on a Pontiac 3x2 setup. Turned out the gasket had a vacuum channel in it and the manifolds shape under the gasket dipped in just enough to catch the channel causing a vacuum leak. He got solid gaskets with no channel and problem solved. I doubt the milling marks are causing the leak. Also see if the gasket covers the bottom of the carb correctly. Hope the way I explained this made sense.
Explained perfectly @BJR. I had the same problem with a Quadra-junk on an old Torquer manifold. Took me forever to figure out it was the gasket...and not the carb. Finally got a gasket that matched the intake (solid) instead of the one that matched the carb.
The only place that indicates a leak with starter fluid is at the front of the carb at the manifold/carb line. Today I will take the carb off and remove the holley metal plate between the gaskets as well as check for warping. Try running without the plate and just one gasket?? Working with a new Blueprint Engines 405 hp, vortec roller cam with air gap intake in my 40 Tudor Ford. Again thank you and I will keep trying. Fourdy
At work we have a “smoke machine “ made by Snap On that is great at diagnosing vacuum leaks. If you could beg or borrow one somehow they are very easy to use. They feed a inert smoke into the intake system and vacuum leaks show themselves pretty readily.
A decent straight edge and a bright backlight then feeler gauges will usually help find wasrped surfaces quickly , anything over .005 can present a problem , under .005 the gaskets should do their job.
Before you take the carb off, look at the offending area with a mirror and flashlight. You may see what the problem is. So if you have a plate in there the stack from the bottom up should be: Manifold Gasket Plate Gasket Carb Make sure the plate is flat, mark up the intake and carb base with layout dye or a Sharpie, run a flat file across the surfaces. Put something in the intake to catch any filings.. don't forget to remove it. Make sure all hardware on the carb itself is secure.
Took the plate off and installed again with one gasket after re-torquing the intake. Check manifold and carb for flatness with nothing apparent with a bright light. Very light rev rise spraying the throttle shaft. (hardly detectable) Okay, take the carb off and put the 80570 Holley from my blown flatty and try it. Viola! Ran and idled beautifully. I could shift the 200-4r thru the gears and have the fan come on without killing the engine even. Spent two 30 minute waiting sessions to speak to Holley tech but now answer. (must be closed for C9) New ?? Where do I start with a Holley that won't idle? Oh, float levels are right on. Runs great from 1000+ rpm on. Thanks for hanging in with me. Fourdy
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