Holley carb leaks

[Norris W.]

For background, I was building Holley carbs as a teenager in the 60's and have always said they're almost idiot proof. I'd guess that counting friends stuff, as well as my own, I've probably done 40 or 50 over the years. Nowdays I can't seem to build one without having em leak all over the intake. It seems like the stains come from the throttle/butterfly shafts, and it doesn't matter whether they're tri-powers from the Corvettes, or just 2 4's from several of my Ford cars. I'm at my wit's end and can't for the life of me figure the fuel source that seems to seep out from the shafts after the cars are run and sit for several hours to several days. In the case of my 500 Shelby, I bought 2 new repop Holleys from Holley several years ago, let the car sit around too much, which dried the gaskets and stuck the accelerator nozzle needles, then when I kitted the damn things leak gas around the shafts. These carbs couldn't possibly have 500 miles from new, so I'm sure they don't have wear on the shaft/plate assy's, but even so seems like this would be a vaccum leak instead of fuel drip when sitting. A friend stopped by today and he's fighting gremlins on a 427/400 he's owned for about 20 years, and suddenly now can't make the carbs behave after kitting, although it's never been an issue before. In the case of my 67 & 69 435's, I've run the secondary float levels as low as the needles will allow without the adjusting nut disengaging, just trying to find a supply source for the dreaded seepage, but still getting the stains. I just can't figure why after all these years, and all these carbs I've never had trouble with, all of a sudden everything I touch now I turn into a leaker. Last month I glued one up with spray on gasket sealer around the NEW bowl gaskets on my 427 Galaxie, just to make sure I wasn't fooling myself with a trail, THINKING it was coming from throttle shafts, and it still stained the intake in several days. Incidentally, I haven't had problems with the way the cars run, just the annoying slow drips and accompaning stains.

Are all kits junk now (both High Grade & Holley), some ghost screwing with all my stuff, or can I somehow have developed a new mistake that I've never had before? At a complete loss. Suggestions welcomed.

[Clem Z.]

Re: Holley carb leaks

i always pressure test the carb needle/seat to at least 8/10 PSI to make sure they do not leak before putting the bowls on the carbs. if the needle/seats hold 8/10 PSI and you still have the leakage problem check the metering body and main body for flatness where they mate together. if necessary press the metering body flat and machine the main body face. check the throttle body for flatness also where it mates with the main body.on corvettes i always suggest you drill a 1/8" vent hole in the gas cap because the heat from the mufflers cause pressure build up in the fuel tank and the later gas caps do not allow the pressure to escape. the front and rear carbs on the 3 X 2 setup use the nitrophyl floats which have a shorter fulcrum arm and they have a harder time keeping the needle/seat closed under pressure. if you do not race the car i would suggest you use a .097 needle/seat instead of the .110. blocking the heat riser crossover in the aluminum intakes is also a BIG help plus you gain some HP

[Mark #28455]

"new" gas

The currently available pump gas is designed for fuel injected motors. In some cases, the 50% boiling temp is as low as about 150 degrees at atmospheric pressure. I have had all sorts of problems with the fuel boiling off in the carb bowls, etc with pump gas, yet when I switch to "racing gas" it runs perfectly. Shut the engine off, remove the air cleaner lid and look into the carb venturis - you may see fuel dripping down from the booster venturis onto the throttle shafts.

Good luck,
Mark

[Clem Z.]

that is why i suggest blocking the heat riser

crossovers in the intakes to cut down on the heat

[Norris W.]

Re: that is why i suggest blocking the heat riser

Thanks for the help guys.