High Oil pressure
 

I recently replaced a cracked head, put in new rings, and main bearings, and have started break-in with 30w non detergent oil. All well, 20+ hours, changed the oil to 30w as my mechanic suggested and now the oil pressure is really high at 2500-3000 rpm's. Do you think it is the oil? should I switch to a 25-40?

92', V6, 4.3 LX
OP is 40 until about 2500 Rpm, then it goes to 60, and at 3000-3500, OP goes to almost 80

Note: during the first 20 hours of break-in the Oil pressure maintained 40, it is only when I switch Oil/filter is when the OP is running high at 3-4000 RPM's.

Re: High Oil pressure
 

You didn't mention what the oil pressure is. Need values at idle and at 2000 RPM.

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Re: High Oil pressure
 

At idle, OP is 40, at 2500 rpm, the OP goes to 60, and 3500 rpm op is pushing 80. Prior to switching to 30w, the OP was pretty steady around 40.

Re: High Oil pressure
 

The new crankshaft bearings should have increased the oil pressure significantly.

Re: High Oil pressure
 

OP is 40 at idle and 2000 rpm. Once I get above 2500, OP goes to 60, and at 3500 rpm it go to almost 80

Re: Help! High Oil pressure
 

Do you think this could be related to the Oil, or new filter?

Re: High Oil pressure
 

New cam bearings too?

Re: High Oil pressure
 

Yes, it has new cam bearings too.

Re: High Oil pressure
 

Give it some time and some lower weight oil. The pressure will come down.

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Re: High Oil pressure
 

Be careful running your engine with higher oil pressures. The oil pressure relief valve will bypass the oil filter when the pressure reaches a certain level. I'm not that familiar with the mercruisers but typically around 70 psi the relief valve will open allowing oil to go across the top of the filter instead of through. Some oil will continue through the filter but it's not a good situation. That's why you should get the oil warm before revving the engine or you'll send junk straight to the bearings.
With all that said, a new top end you would expect a higher pressure 70 to 80 psi with the knowledge that your sending unit could be off by 5 to 10 psi. As long as it remains consistent related to your RPM's I agree with Steve that it will gradually come down as the engine clearances loosen. You could go with a lighter oil which might help some.