holley vacuum leak

[William F.]

My '67 300hp with Holley carb has developed a vacuum leak. It really squeals! I've checked all vacuum hoses/ports and that's not the problem. Carb is tight to manifold-I haven't taken carb off manifold to check anything .Where is leak-air horn to throttle body; I hope not?
Thanks
William Ford

[Clem Z.]

Re: holley vacuum leak

My '67 300hp with Holley carb has developed a vacuum leak. It really squeals! I've checked all vacuum hoses/ports and that's not the problem. Carb is tight to manifold-I haven't taken carb off manifold to check anything .Where is leak-air horn to throttle body; I hope not?
Thanks
William Ford

make sure the carb to intake gasket shape matches the intake manifold opening shape,the holes in the gasket a perfect match to the holes in the intake. check the main body and throttle base plate for flatness as they may need machined

[David S.]

Re: holley vacuum leak

A friend of mine had a similar experience, ended up being the gasket between the intake and carb. For cheap insurance, replace that gasket and see if anything changes.

-Dave

[Clem Z.]

Re: holley vacuum leak

A friend of mine had a similar experience, ended up being the gasket between the intake and carb. For cheap insurance, replace that gasket and see if anything changes.

-Dave

like i posted above make sure the openings in the gasket are a match for the openings in the intake manifold. do not use a full open gasket on a manifold that has 2 round and 1 oval opening. if the manifold has 4 round openings you need a gasket to match

[Tim S.]

Re: holley vacuum leak

Has your car had any service lately or did the wistle come out of the clear blue? You may have lost a carb gasket. Carefully inspect the baseplate of the carb for cracks. The throttle shafts may be suspect. I had one with that. If you were to use a propane cylinder with a hose, you can pinpoint the leak location without making a mess.
Best of Luck!
Tim

[William F.]

Re: holley vacuum leak

No recent service , whistle just came out of blue. If I replace the carb to manifold gasket, do I have to use a new stainless steel spacer that is used on the '67 300 hp engine or can I use the old spacer with a new gasket?How do I pinpoint a vacuum leak with a propane tank and hose(what kind of hose?)?

Thanks,
William Ford

[Tim S.]

Re: holley vacuum leak

You can use the old stainless shim. As far as the hose, anything will do to put on the end of the propane tank. The hose allows you to control where the propane goes to help pinpoint where your are diagnosing. Like carb cleaner, the RPM will pick up.

Tim

[Clem Z.]

Re: holley vacuum leak

No recent service , whistle just came out of blue. If I replace the carb to manifold gasket, do I have to use a new stainless steel spacer that is used on the '67 300 hp engine or can I use the old spacer with a new gasket?How do I pinpoint a vacuum leak with a propane tank and hose(what kind of hose?)?

Thanks,
William Ford

i would try installing a gasket between the carb and the stainless plate as that stainless plate requires a very flat throttle base plate to seal. this worked good on all new flat parts but as parts loose the flatness the seal there is suspect

[William F.]

Re: holley vacuum leak

Could overtightening the wing nut to stud that holds air cleaner top have warped the carb and caused vacuum leak?. I haven't had this car long and have noticed that it's hard to"catch a thread" on stud with wing nut-stud too short or part of air cleaner assembly too tall.

Thanks,
William Ford

[Jeff C.]

Re: holley vacuum leak

Bad power valve. My Brother-n-law had same problem with his 66 350 HP.
Jeff