Holley Help


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Well-known member
May 6, 2019
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My Car
1973 Mach1
Driving home from the tire shop, the wife's car stalled after she tromped on the accelerator then jammed on the brakes.  The car wouldn't start again.  I pulled off the breather and saw the top of the carb was wet.  Figured it was flooded and told her to hold her (foot to the floor and crank it over.  Car eventually started  but was running very rough.  Managed to limp it home, still running terribly.  Told her to keep it running while I looked at it.  No clouds of oil out the exhaust - so not a broken ring, which was my first thought.  Looked at the carb and saw lots of gas dripping off the brass end of the secondary vacuum.  I know absolutely nothing about Holleys but from what I have read, there should be no fuel in that part of the system.  Why is it leaking and running worse than a tractor?  Carb is a Holley 80457-5 on a Cleveland.  Thanks in advance for your help, you guys are way smarter than I am


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So we let the car sit overnight to dry out and tried it again this morning. Had the wife start it as normal, it fired right up but ran very rough. 5 seconds later gas started spewing out of this hole. Stuck float? I'm thinking this is where it was leaking from and just running down the vacuum diaphragm shaft when the car was turned off. Is this a big deal to fix?  Never worked on a Holley. Thanks guys.


Thanks guys. Not a lot of information on the newer 600cfm holleys on the internet. Found a video of a guy troubleshooting a Demon and he said the same thing you guys are saying.  Pulled the primary float bowl  and checked the needle and seat. Seamed ok to me but I took it to my local speed shop and he said you can't tell so l bought his last needle  and seat. Put it in and the car started up rough but smoothed out after a couple of minutes. Probably washed all the oil off the cyl. Walls. The new parts did the trick. I'll  change the oil and take it for a run on Monday. Let's hope that gremlins dead. Thanks again guys.

Also run some "Seafoam" through it and put a half bottle in the tank. This stuff works wonders for cleaning junk out of carbs. That's not to say the worn float needles and seats didn't need to be replaced, that can't hurt for sure.

Combine what passes for gasoline today with cars that sit unused for weeks/months at a time and you gat all kinds of problems. I've seen unusual problems like check pin sticking in accelerator pump circuit, throttle plate sticking shut, and needle and seats sticking open for no apparent reason. Running a fuel system cleaner does seem to help. The one I've found to be most effective is BG 44K. It is a bit pricey at $20.00 on eBay but it works well  with carbs and fuel injection. I also use Sea Foam as a fuel stabilizer. It has worked better for me than Sta-Bil. I'm glad you got it fixed. Chuck


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