hi Guys, kinda new to the forum and could sure use some advise. My '54 235 with solid lifters has developed a noise when hot.

Here's what's going on...after running the engine for about 1/2 hour or driving at 30 mph for 15 or 20 minutes I hear a dull knock!!! I can't hear it at idle only at higher rpm's. Sounds like a small hammer pounding at about 2500 rpm.

I don't hear the noise when I first start the engine at any rpm, when the oil is cold and pressure is 30 - 60#. It doesn't have blow-by or smoke and the vacuum is strong.

After the engine warms up to 180 the oil pressure drops to about 18# at idle and 30# at 1500-2000 rpms. I checked the valve lash (COLD) and found intakes about .006 and exhausts .022. According to my manuals the valves should be set at .008 intakes and .020 exhausts. I assume this is HOT.

Would the valve lash get tighter as the engine gets hotter? Could a too tight valve lash or a bad rocker be making this noise?

I removed the oil pan too (it needed a new gasket anyway) and the screen was clean. I found a few very, very little fine metal particles and only one larger piece of metal shaped like a C about 3/8 inch long, a few thousands thick and a 1/16th wide at most. All the rods have very little play.

Sorry for being long winded but I want to give you as much info as I could.

What do you think? What would you do next? Any suggestions, thoughts you might have would be appreciated.

TIA,
Bob