When I pull up in my fairly newly rebuilt 261 the oil pressure drops to zero and builds up again with a few revs. when the engine was rebuilt a new oil pump was installed. It normally runs about 30 pounds.Any suggestions as to what may be wrong. The engine is in a 1934 master chev. and is connected to the original 34 gauge.
What type of oil filter? A bypass filter must have a restrictive fitting to maintain the proper flow split.
If I'm not mistaken your 34 gauge was for a dip system where it never say 30 pounds and the gauge only went to 30 pounds. Your 261 should be carrying 20-30 even at idle. Could your gauge be damaged from the 261"s higher presure readings? My 261"has 40# at 50-55 mph after warm up and as high as 70-80 when cold.I think I would try a higher reading gauge on it before I started tearing into the engine. That just my opinion. I OL REDNECK
Thanks for the replys so far. The engine is a 1957. It does not have an oil filter fitted. Today I tried an aftermarket gauge and on start up it registered about 42 pounds at about 1500 revs. According to the book I have normal oil pressure is around 35 pounds. I guess when hot.Is it possible the oil pickup is installed incorrectly or could the oil pump be faulty. It was a new one but I never checked it.It only seems to lose pressure when the oil is hot and only when I pull up fairly quickly.
"Pull up" meaning hit the brakes?
Your pickup is uncovered: incorrect dipstick marking, or bent pickup tube. For now, add 1 quart and see if it's better.
Tried adding oil as suggested. Seemed to help although it did lose pressure a couple of times. Not as bad though. The dipstick looks like it may have been played with at some time so will drop the oil and just see how much is in there. Going away for a few days so wont get a chance to play with it for a while. In the meantime if there may be any other ideas I would be glad to hear them.
Thanks Ron.
Every engine I ever used Valvoline in did this. So I quite using it. Good Luck