oil pressure issue?

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bones427

bones427

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I just redone my 340 . and had great oil pressure 80 +lbs. new hv melling pump and deep pan. drove it a few times its ok . went for a cruise and its all over the place from 0 to 30 get it home change oil from break in stuff . now only have 40 to 45 lbs and when you raise rpms pressure goes down. checked with diff.oil gauge, same. check pump drive its good, pulled pan and checked pump every thing looks like new. valve moves free in pump. pulled rear cap to check the plug above its ok and bearings still good and pan is clean so no spun bearings. any ideas?
 
I assume you checked the pick-up clearance when built & and when you took it back apart? That's a crazy change in pressure from new to a few miles use.....especially with no sign of bearing damage or pump failure. I'm not sure what's going on with your engine, but i did run across one many years ago with erratic pressure and the pickup right on the bottom of the pan? Good luck getting her fixed, i'd hate to see your fresh engine starve for oil.
 
Something's funky there. Do any of the bearings look like they got starved? If you haven't, pull them all and check them. I'd also check the lifters and how they look and fit in the block.
 
had a high volume pump on my 340 ran 7000 rpms 140mph lol toss that far as you can

anyways make sure pickup is good check that its not loose or something

check oil pump make sure it's square/flush/tight

check the post above for the plugs behind the camshaft

which oil pan are you running and does the pickup match
 
I've driven many miles on HV pumps with hp springs... Not a problem.
 
why throw hv pump away? deep moroso pan with the pickup to match, yes checked it and pump is square to cap. also sealed it with some permatex. plugs are there, bearings look like new. gonna try another pump.
 
bones427 said:
why throw hv pump away? deep moroso pan with the pickup to match, yes checked it and pump is square to cap. also sealed it with some permatex. plugs are there, bearings look like new. gonna try another pump.
Click to expand...

if you checked everything and it looks good best to double check your gauge(s) and sender or lines also...

is it electrical gauge or mech
 
Did you take a look in the valley at the lifters? If that area's all good then I'd agree with swapping the pump at this point. He's done all the things to eliminate the possibilities.
 
napa/ wix. how many of you guys run a gasket between pump and main cap? I don't think that's it but may try it.
 
bones427 said:
napa/ wix. how many of you guys run a gasket between pump and main cap? I don't think that's it but may try it.
Click to expand...

Yes, the oil pumps come with a thin paper one, I have also traced them and cut them out of gasket paper.
 
I bought my oil pump gasket from T R Walters early hemi parts.
The guy shipped fast and the gaskets were not hardly any money.

https://www.trwaters.com/

Something else to check, have your pickup tube mag-particle or dye pen inspected, there may be a crack that opens up under heat.
 
What weight and type oil do you have in it?
Maybe it's over/under filled or wrong kind and it's foaming now which could cause lower oil pressures?

You could always put back the break-in oil to verify the pressure is good again.
 
it lost pressure with the break in oil in it. was 10-30 vr-1 have also tried 20-50 same issue. checked dip stick with the 8qts and filter. its good.
 
gonna pull intake next. but car runs fine don't think lifter broke but will check.
 
Could be the pump, my buddy put together a 360, good pressure when cold but dropped to 10 when hot and wouldn't go over 30. Pulled it back out, checked everything. Found no problems. Replaced pump and that solved the problem.
 
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