Just pulled apart oil pump on my 540 before closing up oil pan. Found worn rotor shafts and groves in side of pump housing.This was a worked hi volume pump. My question is my engine is built with the bearing clearance on the high side of at or near .003. Definitely going with a high volume but wonder about the new melling with the non cavitate groovs. Will oil pressure be low at idle?

Oil pressure will be too low at idle, may not be damaging, but very uncomfortable when the alarm goes off and the gauge reads 5-10

i use a lot of the 10778 pumps and imo it is the pump you should use,forget about any others.

I use the same pumps in my turbo motors and have no problems

The 10778 C (anti-cav) will have very low oil pressure at idle.

I have this pump in my drag car (565) and my boat (548) and do not see low idle pressure in either. Hot in my boat with 20w/50 idle is still 45 psi plus. I also read about the low pressure at idle but I have not experienced it in my applications.

What RPM idle are you guys running with this pump

IIRC I was idling around 600-700 and clearances were toward the large end of Merc specs.

I am idling around 850

Thanks for info guys