Hello guys. I wonder if anyone can help me diagnose an annoying screech that just recently developed on my 67 442, which had a modified 455 built by the previous owner. I have had zero engine problems since I purchased the car 5 years ago. This season, the car hasn't been driven at all until recently. The only mechanical work I've done this year is change the valve cover gaskets and the car ran fine all last season until I put it away for the winter last November.

The screech appears when the car warms up and will change pitch with changing RPMs. Occasionally it will silence at idle.

Thinking it was belt related, I have removed the A.C. compressor, alternator and power steering belts one at a time. With no belts installed, the screech is still present. I manually turned the water pump pulley and everything feels fine, no slop in the bearing. I also checked for vacuum leaks and snugged down the quickfuel carb as a precaution. Finally, I gave the car a fresh oil change. There was some very fine metal stuck to the plug magnet, but nothing chunky. Almost like graphite powder.

Here is a video link to my Google photos page showing the screech. I'm hoping the link works.

https://photos.app.goo.gl/ExxToNtmpqvb2bAw5

Any ideas for me to chase up before I bite the bullet and bring the car to my local shop?

 

Is it a auto tran, and did you change the filter lately? If so, you may have a leak where the filter hooks up? It will screech and whine.

 

It is a TH400 automatic. I changed the tranny fluid last year, but did not drop the pan or change the filter as it is only about 2 years old. I have an aftermarket pan with drain plug installed. I know sound can travel, but it sure sounds like it's coming from the front of the motor. Hard to pinpoint cause its ear pearcing!

 

First thing I would do is take the filter off and cut it open. That way you can see if something serious is starting to happen and stop running it right now. If the filter is clean then you can keep trying to figure out the noise.

 

Assume you mean oil filter. Nothing out of the ordinary inside the filter. Pics are lousy, sorry.

 

Pull off all the belts, then, start your car. It sounds like an alternator or ac compressor bearing.

 

Yep, that was the first thing I did. Still got the screech

Update: tonight, I did a more careful inspection for vacuum leaks, particularly around the carb. No smoking gun found. In a last ditch effort, I put on some mechanics gloves and started moving hoses and electrical conduits that run along the edge of the intake manifold. Low and behold, I found a pinhole air leak on the right side of the manifold where it mates up to the head. Screeching silences when I hold my finger over the spot. Going to remove the AC compressor mounting bracket and run a fine bead of RTV down the edge of tbe manifold. Should solve the problem.

 

Unless it gets sucked into the engine and causes even worse problems. Try re-torquing the intake bolts and if that doesn't fix it take the intake off and fix it correctly with a new gasket. If it is leaking on the outside how do you know its not leaking on the underside too ? No sense in half ars repairs on a new engine

 

Point well taken Bill. I did indeed torque down the intake bolts as a first step. I figured the risk of any RTV getting sucked into the engine was low as there wasn't a gaping hole - just air somehow sneaking around the gasket in one very small spot. I used high quality Renz-Hienz product very sparingly and allowed it to dry completely before starting the engine to test. Worked perfectly....no more annoying screech. I will certainly pull the intake and replace the gasket when I put the car away for the season. Appreciate everyone's help and advice!

-Steve