screeching small block help.....

Hey there i have a new and when i say new a sbc vortec engine running a new 350 turbo trans the problem i have is when it heats up it has a screeching sound.A new convertor no stall is in the trans i thought it was that making the sound , so replaced it with another same noise.Took belt off same noise so not water pump or alternator. now here is the thing when the engine is shut down the noise carryes on for 2 to 3 seconds weird.i can take the car for a 5min drive no noise but when temp reachers 170 ,180 she screeches some times goes then back again.Any help would be appreciated thanks.

 

Vacuum leak?

 

Thanks cooljunk i dont want to sound like a dumb ass but what is vacuum leak and what can i do to find and fix this problem .

 

Like Cooljunk says, sounds like a vacuum leak, maybe base of carb or inlet manifold loose, split vac hose??

 

Have you replace the radiator cap?

 

Power brake booster or hose to it leaking?

 

A bad intake leak will cause excessive vacuum in the crankcase and in turn will pull air in around the crank seals causing a screech noise.Easy way to find out is to pull out the breather on one valve cover as well as pull out the PCV valve from the other side. Hold your thumbs over each grommet hole and feel if it builds a vacuum to the point it screeches. By the way....its a quick way to find out if your 5.2 Dodge truck lower intake gasket is blown/sucked in.

 

I agree with Ratmotor that it's excessive vacuum in the crankcase being pulled through the crank seals. What are you using for a breather system?

 

Does it burn a lot of oil too? Sounds like a normal 350 to me.



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Belts slipping?

 

You need to find out the location of the sound before anyone can diagnose the cause. A mechanic's stethoscope is a great tool that you can get at one of those cheap tool stores. Alternatively, you can use a long screwdriver or similar tool and hold the handle end to your ear, or you can use a length of thin rubber hose (like a fuel line) and hold one end to your ear.

Any sound that continues after the engine stops seems to be related to either residual suction from vacuum or venting pressure from somewhere.

 

Pull the breather and PVC off the valve covers. It is sucking air through the seals. You maybe have the wrong PVC in it or not hooked up correct.