1987 4.3l 205 high oil pressure

[solar7647]

I have a 1987 Mercruiser 4.3l 205 with high oil pressure, the details are that in the process of doing a restore/refit of my boat I purchased a reman long block from ATK. I swapped all of my tins and manifolds to the new engine and dropped it in. I added conventional 5w30 oil per the ATK instruction for break in and primed the oil pump. I got the engine running and timed properly and it sounds and runs great, I then noticed that the oil pressure at idle was 60 PSI. I allowed the engine to warm up thinking once hot the pressure would fall but it did not. I brought the throttle up to about 3k RPM and the gauge on the dash was pinned. I checked the sending unit and it ohms out at 220ohms, I checked the gauge by grounding the signal wire from the sending unit and the gauge needle pins as it should and is zero when not grounded. I pulled the sending unit and installed a mechanical gauge and it verified the 60psi idle reading and when at 3k RPM the gauge reads over 100psi. I pulled the distributor and ran the pump with a drill and can see oil flowing through. I pulled the valve covers and ran the engine at idle to verify that oil was coming from the lifters. The oil filter is a STP 3980 standard 4.3l oil filter. I have dropped the oil pan to verify that there was nothing in the pick up and pulled the pump, the pump is the High volume M-55 pump. I am planning on swapping with a new standard flow M-55 as what was on my original engine.

Does anyone have any other ideas on what the issue could possibly be, or something else I should check?

Thanks.

 

[Bt Doctur]

Did they install the wrong oil pump ,a hi-vol instead of a reg normal pump.
Defective by-pass spring reliefe.
A hi-vol oil pump requires atleast a 12 Qt pan lest you lose oil at the high rpm`s

 

[nola mike]

Did they install the wrong oil pump ,a hi-vol instead of a reg normal pump.

The pressure wouldn't be higher though, right?

 

[solar7647]

Did they install the wrong oil pump ,a hi-vol instead of a reg normal pump.
Defective by-pass spring reliefe.
A hi-vol oil pump requires atleast a 12 Qt pan lest you lose oil at the high rpm`s

Yes they sent a HV pump with the engine, I didnt notice this when I original installed it when assembling the engine. I noticed last night when I pulled the pump to inspect it. The thing I dont know is rating for the spring in it.

 

[Scott06]

Yes they sent a HV pump with the engine, I didnt notice this when I original installed it when assembling the engine. I noticed last night when I pulled the pump to inspect it. The thing I dont know is rating for the spring in it.

HV pump is not needed. Might also be worth popping a bearing cap and checking clearances. Either the pump has too much capacity and or wrong spring or the clearances are too tight.

Try the std volume pump and see what you get.

This has some points made in question area below the pump specs made for looser bearing clearances than stock - also mentions 70 psi spring

Melling M-55HV Melling High-Volume Oil Pumps | Summit Racing

Free Shipping - Melling High-Volume Oil Pumps with qualifying orders of $109. Shop Oil Pumps at Summit Racing.

www.summitracing.com

 

[Scott Danforth]

what spring is in the pump?

I agree that a high volume pump is not needed in a V6.

 

[alldodge]

The HV pump is what's causing the pressure increase, and from the sounds of it they blocked off the return. Mine has a HV pump but the bearings clearances were adjusted accordingly. Cold idle 70 psi, warm idle 60 psi, above 2500 cold 85 and warm 70 and running straight 40W

Check the remote oil filter to see if there is a valve there or its blocked off

 

[Scott06]

The pressure wouldn't be higher though, right?

Trying to push more volume through same passages requires more pressure

The HV pump is what's causing the pressure increase, and from the sounds of it they blocked off the return. Mine has a HV pump but the bearings clearances were adjusted accordingly. Cold idle 70 psi, warm idle 60 psi, above 2500 cold 85 and warm 70 and running straight 40W

Check the remote oil filter to see if there is a valve there or its blocked off
View attachment 365013

Just curious - How much looser do you run the clearances in this case? Does this provide better longevity at high rpm?

 

[alldodge]

Depends on the motor but in the +.002 area more

Also with a HV pump the heat is increased so will need a larger oil cooler. A cruise I'm hitting 240 to 250 and lake water is 85*. Have a 3 inch x 18 inch cooler

 

[solar7647]

HV pump is not needed. Might also be worth popping a bearing cap and checking clearances. Either the pump has too much capacity and or wrong spring or the clearances are too tight.

Try the std volume pump and see what you get.

This has some points made in question area below the pump specs made for looser bearing clearances than stock - also mentions 70 psi spring

Melling M-55HV Melling High-Volume Oil Pumps | Summit Racing

Free Shipping - Melling High-Volume Oil Pumps with qualifying orders of $109. Shop Oil Pumps at Summit Racing.

www.summitracing.com

Yeah I am going to install a standard volume pump and crossing my fingers that is the solution. If not it looks like a call to ATK in will be inorder.

 

[solar7647]

what spring is in the pump?

I agree that a high volume pump is not needed in a V6.

This i do not know, according the Melling info the pump M-55HV pump comes with a 70psi spring. That is the pump that was sent with the create motor.

 

[solar7647]

The HV pump is what's causing the pressure increase, and from the sounds of it they blocked off the return. Mine has a HV pump but the bearings clearances were adjusted accordingly. Cold idle 70 psi, warm idle 60 psi, above 2500 cold 85 and warm 70 and running straight 40W

Check the remote oil filter to see if there is a valve there or its blocked off
View attachment 365013

No remote oil filter on my engine, its a block mount

 

[alldodge]

No remote oil filter on my engine, its a block mount

ok, but the my pic is the block where either the oil filter is attached or remote is attached. Look in the area and you should not see a plug, you should see something with a ball in the center. That is the relief valve location

 

[solar7647]

ok, but the my pic is the block where either the oil filter is attached or remote is attached. Look in the area and you should not see a plug, you should see something with a ball in the center. That is the relief valve location

AH I got ya

 

[solar7647]

ok, but the my pic is the block where either the oil filter is attached or remote is attached. Look in the area and you should not see a plug, you should see something with a ball in the center. That is the relief valve location

Going through the manual and engine specific searches the only relief vale I can find is the one in the pump.

 

[alldodge]

Is there anything in the filter location like in my pic? Is it plugged like mine or something else there?

 

[solar7647]

Is there anything in the filter location like in my pic? Is it plugged like mine or something else there?

That i am going to have to check once i am home from work, I was just trying to do some research so I know what i am looking for.

 

[nola mike]

Trying to push more volume through same passages requires more pressure
?

The relief valve should limit that though

 

[Rick Stephens]

Back a gazzillion years ago I did a rebuild on a ford F350 351 Windsor. The machine shop included a HV oil pump. Pressure was so high it would shear the roll pin holding the distributor gear on. Which didn't care if you were in high speed traffic or at work in the parking lot, stopped the truck right there. For a bit I ran a 1/8" diameter piece of 7018 welding rod in there instead of the roll pin, which of course worried me I'd just bust the gear apart... Finally just took it apart and installed a standard pump, which is probably still running 30 years later.

Unless everything is spec'd to run that thing, it is useless.

 

[Scott06]

Yeah I am going to install a standard volume pump and crossing my fingers that is the solution. If not it looks like a call to ATK in will be inorder.

Strange they would send a HV oil pump if the engine wasn't set up for it....

Would verify the relief AD is speaking of, i think with out the remote filter it is in the Oil Filter adapter/threaded piece that attaches to the block