Help with engine chirping noise

[Lattimer]

I have a 350 crate motor in my truck, about 5000 miles on it now, and I have developed an intermittent chirping noise that I can't seem to locate. Engine is a 1-piece rear main block with Vortec heads, aluminum manifold, 625 cfm 4-bbl. Manual trans, stock style clutch rod setup.


It doesn't make the noise at all until it warms up.

Then the noise will come and go. By ear, it seems to be on the left bank of the engine. In gear, in neutral, clutch in, clutch out, on brakes, off brakes, makes no difference. Chirp is definitely tied to RPM, gets faster as engine revs. Also gets louder as engine revs.

Alternator, water pump are new. PS pump recently rebuilt. Electric fans so its not a fan clutch. I have tried spraying and soaping the belts. All parts are new in the last year. Standard v-belts. Replaced the header gasket yesterday as a guess, and still nothing.

I can't seem to find it with a stethoscope, everything I touch sounds normal. I have checked the water pump, PS pump, alternator, every inch of the top end. Valve train sounds normal. Can't seem to find a vacuum leak, tried the carb spray all over and found nothing. Can't hear the chirp at all with the stethoscope.

Sometimes if I turn the truck off and restart it, the noise is gone. Other times it comes right back. Sometimes while idling at a light it will stop, then comes back when rpm's come up.

Other than the noise, the truck runs great. Starts easy, idles fine, great power, etc. No other funny noises.


Hoping somebody can offer some ideas to check! Thanks in advance!