Holley Vacume Leak

[William P.]

Hi All,

I have a 71 LT1 small block with a 4801 Holley . The engine runs and idols perfect untill it fully warms up . Then it develops a vacc leak and idols poorly . I have changed the base gasket and the gasket between the throttle body and the carb body. I have also isolated all the other intake vacume sources with no success .

Thanks in advance for your help !

Bill

[Timothy B.]

Re: Holley Vacume Leak

William,

So you are saying after the choke blade opens the vacuum leak is present and noticeable in the way the engine idles.

I would remove the front and rear metering bodies and throttle body (base) and take a piece of sheet glass (very flat) with some 220 wet sandpaper and carefully plain the bottom and front/back of the main body. The glass measurements are in the archives, I don't remember them. A machine shop can do this for you if you take it apart.

Also it's a good idea to plain both sides of the base but be careful removing the staked in screws that hold the throttle blades, if you break one..

With all surfaces flat, tighten the screws but don't overtighten. Maybe a drop of blue loctite on the base screws. Sounds like your carburetor may have some warped surfaces, hopefully the metering block is flat and new Holley gaskets will seal these passages again. Use Holley gaskets..

[William P.]

Re: Holley Vacume Leak

Thanks Tim, I will try your advice .

Bill

[Jim T.]

Re: Holley Vacume Leak

William I am not famililiar with your actual Holley however if you have a vacuum unit on your Holley for the choke, it could of developed a rupture and is sucking air into the carburator since it has a full time vacuum line connected to it.