Well Ive been chasing an oil pressure issue with my fresh built 370. Started off at 60psi idle oil pressure with a tick ported ls6. Ended up washing the piston rings so I had to take it apart and rering it. All the bearings were perfectly fine so I reassembled start it up with same oil pump and pressure. Take it to get tuned and suddenly 0 psi. I thought maybe the pump took a dump. I went and got a melling high pressure pump. Put the pump in fire it up great 55 psi at hot idle motor is quiet nothing in the oil. Take it down to my tuner start street tunning and I notice the pressure starting to die off (about 5psi every 10 minutes). Take it back to the shop, turn it off, start it back up suddenly pegged at 0 psi. Now I start thinking maybe I should replaced the galley barbell as its never been replaced in an old *** iron block. Do that start it up I now have 25 psi. Drive it for a few minutes fades off to nothing again. I am stumped. There is nothing in the oil, no noise from the motor. Im about to pull the motor again but I dont know where to look at this point. Im thinking possible spun cam bearing but I figure i would hear it and thought it wouldnt slowly fade and would just drop to nothing if that were the case.

Engine was broken in with comp 10w30 break in oil, have been using mobil 1 10w30 since

motor specs:
wiseco pistons
compstar 6.125 rods
arp everything
clevite bearings
mamo 235 heads
custom crind mamo cam
btr pushrods
yella tera roller rockers
melling oil pump
c7r timing chain
cometic gaskets
stock crank
lunati link bar lifters

FAQ:
its not the opsu, ive replaced it and have since switched to an autometer gauge.
oil pump oring is correct and not pinched
cam retainer plate is brand new
oil galley plugs are brand new
oil pick up and pan are brand new
issue happened with 2 different brand new pumps
engine was freshly machined, balanced, and plasti gauged

 

I'll post a pic of the cam bearing that came out of the rebuilt 6.0 that was in my car when I bought it. Same-ish scenario as you. Oil pressure was good then all of a sudden, nothing. No noises, nothing worth worrying about in the oil, filter or on the drain plug. Motor still ran fine other than the oil pressure dropping off to nothing after it got warmed up. Replaced OPSU first, no change. Checked with two different mechanical gauges to verify, checked out and the dash gauge was pretty spot on with the mechanical so I decided to try oil pump since the motor still wasnt making any noises or debris in the oil to indicate other problems. Swapped out two different pumps, a brand new LS6 first then a Melling M295, still no change. Decided to yank the motor and found this....

 

It is going to be an open in the motor. I would expect a cam or main bearing, Generally rods will make a lot of noise but in some rare cases you will not hear them. The motor is mechanical, this means nothing changes. If you are loosing oil pressure with heat the oil is thinning out and finding the largest hole to escape from (Loss of a bearing). I know you probably don't want to hear this but you are going to save a lot of time to pull it and inspect. If you have no metal in the oil you likely just have a bearing that is the wrong size somewhere (something like a std bearing on a .010" crank).

If you are still having trouble give us a call and we can help you troubleshoot the issues.
Thank you,
Kyle
Thompson Motorsports
972-853-2450

 

did it mangle your cam? Id hate to have to order a new one it took for ever for my custom grind to come in.

 

Yes, the cam was completely trashed around that journal. I'm still not completely sure how the motor wasnt making some kind of god awful noises with how bad that bearing was chewed up and wrapped around the cam. I wasnt planning on salvaging anything from that motor other than intake/accessories and covers anyway so the old cam being trashed didnt bother me. It was an unknown spec cam when I bought the car so I wouldnt have reused it in anything else even if it was OK.