I bought a rebuilt flathead 8BA(have receipts and everything). Did the 20 minute beak in period. Noticed oil pressure was good at startup, and it seems as it heats up, the oil pressure drops to 20 at about 2500 rpm and about 5 at idle. Did some researching an thought maybe the rebuilder left the front galley plug out. I ripped timing cover and gear off to check, and its in. I broke the motor in with vr1 10-30 along with a break in additive. Does this sound like a bearing/clearance issue? thanks!
A couple of other possibilities-- Fuel pump push rod bushing OK? Do you have an original oil filter system?. If so, make sure it has the proper restrictor fitting in the feed line. Bob