I ran my '56 235 for about 30 min. today and the needle on the Stewart oil pressure gauge that I installed in the side of the block began to vibrate rapidly about +/- 5 PSI in time with engine rotation AFTER the oil was hot. That is, it vibrates slowly at idle and vibrates faster as engine RPM increases. It did not vibrate when the oil was cold. Pressure is 40 PSI when hot. Oil is clean Rotella 15W 40.
Could this indicate a bad rod bearing? I visually inspected the main bearings before I started this engine and they looked OK (I did not mic them) so I didn't pull the rod bearings.
