im running this pump in my 383. its a mellings 55a i think. the oil pressure seems kinda high 45 psi at idle and my timing is +/- 2*. ( think the pump may be causing the eratic timing) what pump would you recommend for my application. this motor may see 7000 one day. Dave

Sounds fine to me. GM stuff is hard to beat. Those pumps worked fine in 302's and their max power wasn't till 6800+

a Z/28 pump is a stock pump with a higher pressure relief spring. It's not a HV pump, which are not needed or helpful in a SBC unless your machinist/crank grinder is still living in the 60's and grinding in .0035 clearance.

is that pressure at hot idle? like after a few miles on the road? That would seem a little high. If that's the hot idle pressure what is the cold idle pressure?

Tom the cold pressure is 60 with 5w 20 mobil 1. ive never really looked at the gauge except after lifting after the stipe and im still over 70 psi.

FWIW, might get a look at the mounting neck on this pump as there was a change in pump design that resulted in some broken necks below the bolt mounting, thus allowing pump to drop into pan. Vibration from severe duty may have to do with this. I understood the fix was going to the Select Series pumps bearing part #'s 50xxxx. Mellings made the change as per request from GM but has since corrected the issue with their Select series.

Tom the cold pressure is 60 with 5w 20 mobil 1. ive never really looked at the gauge except after lifting after the stipe and im still over 70 psi.
Have you verified that your gauge is accurate?

I thought the Z-28 pump not only had a different spring but slightly larger pump gears inside as well as having anti-cavitation slots and balance slots in the housing cover? Maybe I'm thinking of an aftermarket piece.

Dave

I put an M55 pump on a fresh 350. The pump I got is supposed to be stock, and the bearing clearances were on the tighter side of the mean, but I'm still wondering if the pressure is a little too high. It puts out 70 cold and 45 hot at idle. I know that only .001" difference from one engine to another will make a big difference in pressure, so it might be normal.

I thought the Z-28 pump not only had a different spring but slightly larger pump gears inside as well as having anti-cavitation slots and balance slots in the housing cover?
Chevy did NOT use larger gears, or anti-cavitation slots in the Z-28 pump.