Chrysler Marine 440 Rebuild w Low Oil Pressure


New member
I rebuilt my 77 440's a couple years ago and I noticed on one engine at first startup that it had a bit lower than normal oil pressure at cold start than what I would have expected. Instead of the typical 60 psi, I got 40-50 psi. Still ok but not clear why it was a bit low. The rebuild engine had all the usual stuff - new bearings, gaskets, seals, timing system, Melling oil pump, pistons, rings, etc and a new Edelbrock 1409 marine carb. Using 10W30 oil currently. Aside from the carb, all stock parts. Engine ran well except the oil pressure concerned me and the valve train seemed a bit "clacky" compared to my other engine.

Fast forward two years (with little use) and this is what I am seeing....

Cold start sees about 40-50 psi, then drops to 20-25psi once warm. I have been running the engines easy at 2200rpm max due to the oil pressure issue. I put a mechanical pressure gauge on today to confirm what I was seeing on the console gauge. Wiggles a bit when running but clearly < 20 psi.

What is really puzzling me is that rev'g the engine I see a slight DROP is oil pressure. The opposite should be happening! - So why is this happening?

My thinking is this may be due to:

- bad bearings (on a rebuild with < 50 hours all checked w plastigauge at install? seems a stretch)
- [stock] pickup tube is above the oil level and cavitating (however, dipstick is full; added another 1/2 qt of oil no change)
- oil pump pressure relief valve is stuck open

I'm leaning towards the oil pump as my problem (all along) and about to pull it off.

Other ideas?
Ya, thicker oil is in the plan regardless. These engines originally (mid 70's) call for SAE30 oil and I've been using 10W30 mainly because 30W oil is getting harder to find. 20W40 seems like a good choice for the future but for the moment, it is only a bandaid solution. If the oil pump replacement/fix does not solve this, I think it points to internal issues like a spun bearing(s) and thicker oil will have to suffice until I can pull the engine to take a look