No oil pressure, new build

[fast72beeper]

The fresh 388 we just built for my sis in laws 86 GMC has a oil pressure problem. Motor had 70 lbs when cam break in was started. During the break in pressure slowly dropped to 40 lbs. After break in motor had about 20-25 at idle out of gear. In gear it has none.

Changed gauges, no change.

Verified that the plug is under the rear main cap, so I pulled motor out and tore it down.

Expected to see bad bearings....not the case. All bearings look good. Clearances are all fine. 1.5 on rods and mains. Plugs in front side of block are all seated. Cam bearings, journals look fine. Bypass in filter housing appears to be good.

Oil pump seems to be OK. Rotor clearance looks (havent measured, but probably .002 or so) good. Pulled relief spring out and it seems fine. Havent verified that the plunger is moving freely. Probably will let the machine shop look at that.

Checked block thoroughly for cracks in valley/galley area. Cant see any.


Ideas on where to look next?