Re: Big Chevy Oil psi low in mid to high rpms?

spannerx — Tue, 11 Nov 2008 11:25:05 GMT

Mate im having a similar problem with a 6 cylinder nissan rb 30 engine my oil pressure moves up and down by up 20 psi at a constant 4000rpm drops from 70 psi down to 50 and back up again as if i;ts sucking air, the oil tank is in the boot and the peterson pump seems to be working overtime .

Re: Big Chevy Oil psi low in mid to high rpms?

pat mccarthy — Sun, 10 Aug 2008 01:50:13 GMT

the 10 psi pre 1000 rpm is not really worth much i have built many bbc that only made 65 psi as long as it is going up with rpms and not droping you are ok you would wear out the dist gear and wast HP trying to get more psi would be a very good idle to put the windage tray back in to have some oil control at hi rpm

Big Chevy Oil psi low in mid to high rpms?

ckmate88 — Sun, 22 Jun 2008 11:28:18 GMT

I have a Gen 4 454 30 over / has an M77 Moroso oil pump w/ welded and bracketed pick-up with 50-65 psi @ idle / cold or hot, oil pressure drops to around 10-20 psi after 28-3K rpm. Bring back to idle / 50-65 psi immediately w/ 20/50 or 40 w oil. A mention of pickup to bottom of oil pan was made / oil cooler system failure (22” cooler) w/ 12AN line / not having windage tray / bearing clearances…..so on. The machine shop suggested thin oil (5-30w) to test the theory of pick-up clearance and can run thin oil due to tight bearing clearance. The oil psi would stay around 30-40psi cold at 28-3K rpm then drop to 10-20 psi hot @ 3K- 4K rpm. One rule I understand is 10 psi for each 1K rpm. There is 3/8 clearance off the bottom of the pick-up to the pan and crank clearances are @ .0018 rod and mains. The remote oil cooling setup has been removed and the adaptor plate was re-installed with a screw on “ WIX and/or AC Delco” filter to the block. I hear Fram is bad. This test resulted in the same oil psi. The distributor has been checked with grease in the end for set clearance to the pump shaft. This clearance is not a problem. This engine never had issues rolling down the track @ 7200 RPM w/ 60-70 psi all day w/ no windage setup. This block was pulled to inspect the crank (which was fractured) so block met the engine stand until now / cam bearing not replaced. So far no metal in the oil filters since break-in ten hours on motor running. The only change has been the oil pan, crank and cam. The oil pan I ran before @ 52K all day long with out oil psi issues but with a stock oil pump and 330 HP big block and small oil cooler. This pan has a baffle/dam setup with I think a ½” to ¾” cut down the middle to allow oil transfer to the back chamber. This is the second pump same issue. I’m getting ready to add two stack breathers as I only have one Mopar breather in one valve cover. There is 12 qt’s of oil in the system so far and I’m reaching for suggestion at this point. The Machine Shop that turned the crank and conditioned the rods for me is stumped at this time.

Thanks,

Scott

ckmate88

Technical

Re: Big Chevy Oil psi low in mid to high rpms?

Re: Big Chevy Oil psi low in mid to high rpms?

Big Chevy Oil psi low in mid to high rpms?