g741.org

Sounds like it's coming from the dizzy. I don't think it's the generator or water pump. This is at idle:

https://youtube.com/shorts/xtPJqD4p7LM?feature=share

Anybody got ideas?

How about the clutch area? Try depressing the clutch pedal slightly while running to see if that makes a difference.

Same noise with the clutch in or out

There was a lot of competing or background noise in the video. Is it possible to separate out or filter the sound?

Could be a worn camshaft, oil pump issue, valve lifter, distributor, generator or water pump bearing, etc, but go simple first.

What about the belts? Are they in good shape?

Pull the belt and see if it goes away. Quick and eliminates a bunch of items.

ashyers wrote: ↑Thu Apr 11, 2024 4:42 pm Pull the belt and see if it goes away. Quick and eliminates a bunch of items.

Excellent suggestion!

To me it almost sounds like high pressure air leak. Time for a quick compression test

Perhaps a manifold leak?
Gary

Go get one of those cheap auto stethoscopes and simply touch each component. When you hit the right one you will know it!

Excellent suggestion, Murf.

Now, I'm off to play doctor with my truck.

Same noise with the belt off, and after torquing the manifold (several nuts were loose).

greeno wrote: ↑Mon Apr 15, 2024 6:10 am Same noise with the belt off, and after torquing the manifold (several nuts were loose).

Any luck finding the issue?

Yep on the stethoscope.

Many years ago at the Yuma Proving Ground DRMO, a very pretty M37 was sold with a description "engine rod knock".

A friend bought it, and it turned out the generator bracket was cracked, causing what really did sound like a rod ready to come out.

PoW

I changed the break in oil (30w) to T4 15w-40 and the noise is gone. It’s been in there 2+ years but very low miles.

Wow-I know some differentials require an additive but wouldn't think changing the engine oil alone would solve the issue.
Thanks for letting us know!
Gary

Poor man's stethoscope: get a piece of old broom handle or a similar size metal bar. Put one end on the engine part in question, and the other end against your ear. Works well to isolate sounds from different parts of the engine.