Chrysler 313 motor oil pressure issue.

Recently rebuilt Chrysler 313 in Dodge Power Giant the oil pressure when warm drops to 25psi on acceleration and raises 25 psi to 50psi when you lift foot off accelerator. Only needs slight touch on accelerator when coasting to do this. Mechanical gauge and checked with seperate master gauge giving same result. How can this happen?

Check the oil pump pickup screen. I had a similar problem with my Morris. Start up, showed 60 lb but on acceleration would drop to nearly nothing. After checking the relief valve which made no difference, I pulled the sump and found the screen was nearly blocked. Oil could get through at low revs, but not fast enough when revs increased. Cleaned the screen and now 70lb on start idle cold and drops back to 60lb running when hot.

A google search suggests the oil pickup might be too close to the bottom of the sump?

Yep as above


Paul

What you are telling me is that on acceleration the oil pickup is too close to the sump and when you deaccelerate the pickup moves away from the sump. How does that happen?

WAG
Oil gets  pumped to the top ............ oil galleries are blocked that returns the oil to the sump
there by slowing the oil to return down South
BWEK
cya

You are missing the point....the oil pressure falls on accelaration and raises on de acceleration yet the oil pump which is gear driven is going at the same speed and is in no way connected to throttle setting. The block was hot dipped when rebuilt so all oil passages would be clear

Recently rebuilt Chrysler 313 in Dodge Power Giant the oil pressure when warm drops to 25psi on acceleration and raises 25 psi to 50psi when you lift foot off accelerator. Only needs slight touch on accelerator when coasting to do this. Mechanical gauge and checked with seperate master gauge giving same result. How can this happen?

How can this happen?

One as mentioned by others.  The inlet of the pump is partially blocked and the pump is cavitating at higher engine speeds.  (or an after market pump with a to high flow rate that doesn't match the gallery/inlet flow rates, again causing cavitation.)

Two,  as described in the quote, with some light throttle or heavy throttle, there is end play or other movement in the bearings, cam or crank allowing the oil to leak

Three, the engine hasn't been assembled properly and a 'fissure' is opening.

Yank V8s generally have floating pickups .....Id certainly drop the sump and check everything is OK.

When you say acceleration, is this out and about on the road ?
Or just sitting giving it a boot full

I need some more detail before I can offer any advice


Paul