The Stovebolt Site Forums The Shop Area Engine Shop Oil Pressure Weirdness Part Two

I made some head way today on my sudden loss of oil pressure in my 261 motor. Cold it's at 50 psi and warm it is 15 psi and on level ground it will sit there all day idling and not lose pressure, drive it up a steep hill and its fine stop and sit on the the steep hill and it's OK but let it roll back a few feet and jamb on the brake and the pressure drops to zero. which tells me the oil pump pick up loses the oil and sucks air. Roll it back to level and start it back up and it's fine again.
I've been putting 6 qts. in it normally but by adding another the the problem lessens. Now another thing is the dipstick has low and high marks on it above the factory ones from one of its previous owners as if either the stick came out of a different truck or they ran a higher level of oil possibly because of the oil filter. It looks like 8 qts would meet the revised high mark, is it possible there should be 8 Qts in the motor? this engine came out of an old school bus but all the 261's saw heavy truck use when new. I don't want to over fill it as it will blow out the road tube.
This problem has me going, an online manual says six quarts. Is there maybe something else I'm missing here?

-Mike-

7qt if you emptied/replaced the oil filter.

What year 261?
What oil filter?

1958 With a full flow filter and last oil change not that long ago I did empty the canister and replaced the filter and then put a total of 6 quarts in with the understanding that was with a filter change, so according to your spec. I was a quart low from the get go!