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350 Crate Engine: Loud humming sound after engine warms up

3K views 2 replies 2 participants last post by  sofa1515 
#1 · (Edited)
I was wondering if anyone could help me troubleshoot a loud humming sound on a new 350 crate engine (85' gmc pickup)? Everything sounds and works great when I start the engine...but after a few minutes (engine warms up) I get this fairly loud humming sound.

I have all emission hose connected.

When I lift the PCV valve out of the valve cover the sound goes away.
I check for leaks around the base of the carb and looked for cracks in any hoses, but didn't not see anything...

Pretty much everything on the engine is new: carb, intake, headers, valve covers, distributor, etc.

Any ideas or tips would be greatly appreciated!

Thanks
 
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