motor whistle

[jercasche]

I just finished the swap of my 2bbl carb to a 4 bbl carb and intake. My engine starts whistling after about 1 min of running and does not stop. I think it may be the square hole spacer since my carb and intake both have 4 holes. The spacer has a needed vac port for my pcv valve. Could this be the whistle?

[chris401]

Holley? Does the whistle quiet down just off idle or more throttle?

[jercasche]

Yes it's a Holley. I changed to the proper spacer with 4 holes and the whistle got quieter. It seems like it runs about a minute and then starts. It could possibly be my exhaust manifold on the passenger side.

[chris401]

Holleys are known to develop vacuum leaks between base plate and main body. You can block off the rear idle channel s with a couple of set screws. If your whistle goes away or gets quiet in the rainy or humid conditions it may be the PCV port in the center. Rounding the edges off with a file should fix it. Stack your spacer and carb together and see if any gasket is smaller than the bore. That can cause a whistle also.


I had a one off problem once when I mated a 600 base plate to a 390 body. The transition around the edges of the smaller bore whistled it's worst in dry weather. Found another 390 base plate to match the main body and the whistle stopped.

[bruceandersson]

You can carefully spray carb cleaner around the base of the carb while idling to see if its a leak. If the sound changes or engine speeds up, you have a leak. What's the vacuum reading at the manifold?