sbc high oil pressure
 

On my ski boats 350 last year before winterizing it I was changing the oil and accidently filled it with 20w-50 when I started it I noticed higher than normal oil pressure. I thought no big deal next year I'll put in 10w–30 and it will be normal. So this year comes I change the oil and the pressure is still high 55 at idle and over 90 if I rev it.

Ive tried two different mechanical gages
Tried installing a new oil pump and filter bypass

The motor has 120 hours runs like a top and had zero shavings in the pan

Im thinking a bearing has spun and is bloccking an oil hole

Any advice?

what route does the oil take? Cam or crank first

fixx
 

oil goes through the main's first and then the mains feed the cam bearings.

did you change the filter at the same time ? or have the lines off or anything like that ? if you changed the filter, i would change it again on the theory that things like this that work before you do something and then don't are always " what you did last" beyond that it sounds like the oil pressure relief valve is jammed closed but nothing on this planet would make that happen just by changing the oil...

Yep I've changed filter again from a delco to a k&n and I swapped the filter bypass valve at the same time. It's not a remote filter so no lines to mix up

Yoda,
Which oil pump did you use ? The filter bypass really has nothing to do with oil pressure. If you are "truly" getting 90 lbs, I would think that the bypass valve in the pump is stuck shut, unless you used some type of high pressure pump, but even those dont generally make 90lbs.

Yup, I know, its a new pump, but that dont mean squat.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

i shimmed a dodge slant six bypass once. blew the oil filter apart in 5 seconds. my vote goes with pump bypass. while you are in there, check the mains and replace the rod bearings.

I just pulled it apart mains and rods look like the day I put them in. I think I'm going to put in a used pump I have here just to see what happens. Both pumps are melling the original was a high volume. The new one is a standard flow m-55
Thanks for the responses

Neil

I've been thinking about the relief valve on the pump if it was stuck closed wouldn't I only see high pressure at higher rpms? Or is the relief valve opening all the time on a normal engine.

fixx
 

did the pump come with another spring? usually the pump comes with the high pressure spring installed already..if it came with the extra spring then take i think the purple one out and install the lower pressure yellow spring,,this should give you cold 60 psi and 25 psi hot at idle..

That is only on Big Blocks and it is the other way around, they give you the HP spring to install if you want to.

Yoda,
The relief valve is open almost all of the time. I forget the number but I was talking to George at Melling one day and he said that the pump would pump an ungodly pressure without the relief valve.

the slant six i shimmed the relief valve shut. i watched the oil pressure guage peg and heard the oil filter blow in 5 seconds at IDLE. so that relief valve is the problem.

fixx
 

correction,,i was tinking of the m55hv..that pump came with a low pressure yellow spring..

*update

After changing the oil pump, inspecting the bearings and having the oil pressure be the same. I decided to just run it so I did at idle for an hour since then its been fine and the oil pressure wont go past 75 now