QuestionOIL PRESSURE PROBLEM. 40 POUND START UP COLD 10@150 DEGREES NEW RODS ,NEW MAIN BEARINGS, WAS CHECKED .003 CLEARANCE. AFTER ENGINE WARMS SLIGHTLY OIL GAUGE BOUNCES UP AND DOWN. AT 2000 TO 2500 RPM YOU CAN HEAR CRANK SHAFT RATTLE. OIL PRESSURE COME UP BUT STILL BOUNCES. OIL USED IS CASTORAL GTX 20-50.
AnswerHi David,
Even though .003" is a little excessive many race engines use that along with a high volume oil pump and have more then 10 PSI at 1500 RPM and above. 10 PSI might be expected at idle.
Places that you can loose oil pressure are cam bearings, rocker arm bushings and possibly a problem with the pressure regulator valve and spring.
I do have concerns that you have .003" with new bearings. You should have miked the crank for size and for out of round on mains and rods. Then used plasti-gauge to confirm clearance. With a good crank you should have seen from .0015" to .0025" on the mains and from .0015 to .002" on the rods.
20w-50 oil is a little thick for new bearings too and should have shown better oil pressure then what you have for .003" oil clearance.
Even though an oil pump can be worn I have never seen a Triumph with low oil pressure due to a worn pump. I have seen worn oil pumps that have the pressure regulator valve stuck closed go to excess of 350 PSI on a rev up and explode a spin on oil filter.
I would check the pressure regulator valve and spring first and then look at the volume of oil at the rockers to see that it is not excessive indication badly worn rocker bushing or even something wrong at the rocker shaft.
If all that is correct I would pull the crank and cam and start close measuring because that engine will surely self destruct making bottom end rattling noises and only showing 10 PSI oil pressure with the thick oil you used.
Howard
