The 340 I put in my Duster made 75 psi when I primed it with an air drill on the stand. It made 75 psi cold at idle when I started it up 3 weeks ago. Warm it made 45 at idle and 75 revved up some.

Today I fired it up and it was making 80 cold at idle and 95 just off idle. Warm it was at 60, and 80 revved up.

Should I be concerned? It has 10-30 Pennzoil in it, and it was in the low 60s today. It was in the mid 70s when I fired it last time, so I wouldn't believe temperature to be an issue.

Thanks!

95 is pretty high. Apparently you have a quality oil filter or this would be a DAMHIK post. Is it possible the relief valve is sticky? Try a new oil filter perhaps?

Sounds to me like a lot of oil pressure I would verify with another gauge... would be my first step

That's a lot of pressure for 10-30 warm big D, but I would just keep monitoring it for now. Changing filters is a good idea - and maybe cut the old one open.

It'' got a NAPA Gold filter on it, I let it run for about 20 minutes and it didn'' balloon it.

I don'' think it'' the gauge, but it is an older Autometer mechanical.

I will fire it up next weekend when I am down there again.

Thanks guys!

20 or so years ago when I was building sb mopars for one of the oval track teams, I found that in those things, the melling high volume pumps would almost always produce over 100psi of hot oil pressure at rpm. I had a couple that were close to 140.

No real clarity from melling on why this was, but installing std pumps cured it.
They were 75-80 hot oil pressure at rpm.

I never had any issues from the high oil pressure. Those motors all ran thousands of laps and I never had any of them fail from an oil related problem.

I had the same thing happen on several Melling SB Mopar high volume pumps, they had the BB bypass valve in them
I pulled the retaining plug and install a SB valve and new welsh plug was all it took to fix it
The trials and tribulations of engine building

I am just guessing it may have a chunk of crap stuck in the relief valve or something. I did change the pan and put the original pump back in the motor before I put it in. (When I had the motor in my truck I used the truck pan and pump on it.)

At least picked up oil pressure from when I fired it, if it would have lost 20 I would be really concerned.

Was at the shop and fired the Duster and moved it out to warm up. Had 90 cold at idle when I put it outside.

Moved some other stuff around and checked on the Duster. It is now back to 30 hot at idle and 75 revved up a little.

Hoping to be able to get the rear under it before too long and get it to the track.

Melling has had that issue with sb pumps for a LONG time
some had BB relief some had hole for it drilled .100 thou shallow thus like shimmimg--it never ends
I fired a new one up yesterday--it did not prime up "tight" but wth fired it up no oil pressure after all the trouble tear down etc it was a defective new pump---pumped like a squirt gun--new pump and a 20 hour thrash and it all looks good today--an UNPAID thrash
Some days I just want to go get a job selling golf clubs and never mention engines ever again

OUCH!