69 mustang engine noise

I just notice my engine doing the same thing, but at idle. It does sound as if its coming from the thermostat area. I used a stethoscope to try and isolate the noise. Although my alternator was noisey, I could not hear the knocking sound on anything I probed, including the engine block. Keep looking and let me/us know what you find, I will do the same.

No, it is not valve train noise (351W with hydraulic lifters). The noise is intermittant.

The cam thrust plate could be worn, did you check cam end play when you re-built? you should have 2-6 thousands clearance.

Does your thermo housing have a large brass, screw in over temp/pressure. spring housing in it?
The cam is directly under the intake, the thrust plate is behind the timing chain and gear cover, on the front of the block, just below the thermo housing (I'm assuming your thermo housing is in the front)
The thrust plate is flat and shaped like a football.
One hole in the center for the cam, and a bolt hole on either side.
The thrust plate is put on before the cam timing chain gear.
The cam has a thrust surface on the front bearing journal, the cam is slipped into the cam bearings in the block, and the thrust plate is bolted to the front of the block.
This keeps your timing gears and chain running parallel or true, and also keeps the cam from moving backwards and forwards, and the intake and exhaust lobes are directly under the appropiate lifters, or tappets. Many people don't think to check cam thrust; clearance is only 2 to 6 thousandths of an inch. Worn timing chain and gears, over a period of time, can wear down a thrust plate (which keeps the cam from moving back and forth)
If the thrust plate is worn, it is symetrical, so, all you have to do is flip it over to the other side. I am not questioning your mechanic's knowledge......just trying to help!

Can't say without checking the engine myself. I'd hate to see you cause some terminal damage by beating it all week-end or something like that. If its been apart and back together twice and nothing can be found wrong... I'd say keep running it normal!, and see what happens. Maybe it will break-in, and the noise will go away. Good luck! hope you find a solution.

I have the same noise. Exactly what you described...two rocks clicking together. It was my thermostat. I removed the thermostat and the noise went away.

Solid Lifters adjusted at .020 (double checked) and kinda noisey, but the noise your talking about was definitely not cam thrust or valves....like you said...two rocks clicking together.

Hope it's your thermostat!

If the noise went away with the stat removed,check the housing to make sure when it's tightened down it holds the rim of the stat in contact with the intake,the only other thought is to check if equipped with a circulating pump-the vanes in the housing-one might be broken and bouncing around inside the pump housing.