New engine with low oil pressure ? UPDATED READ NEW POST !!

RAYMONDH

I just had my 390 rebuilt by a good local shop. Everthing is new. At first start up with the EOS oil additive ( to be save ) i had 55 psi of oil pressure during that break in time. When i drive and hit 190 in water temp it will be about 40 to 45 psi while at cruising speed. I have a big cam and if i set the idle at 700 rpm it drops to about 10 psi .So i set it at 1000 to keep pressure at 20 .I hear people with 75 psi and at idle having 35 psi .The engine has 100 miles on it and i am hesitant to continue , any ideas?

JERSEYJOE

YOU SHOULD HAVE 20+ AT IDLE WITH NEW PARTS.AND 55 TO 60 DRIVING DOWN THE ROAD. DID YOU REPLACE THE FRONT COVER? AMC'S WITH MILES TEND TO WEAR THE ALUMINUM COVER AND THE CLEARANCE BETWEEN THE OIL PUMP GEARS AND THE COVER EXCEED LIMITS. ALSO THE GEARS TEND TO EAT INTO THE OIL FILTER ADAPTER AND THE END CLEARANCE GOES SOUTH. THIS WILL APPEAR AS GOOD PRESSURE COLD AND LOW PRESSURE HOT.

RAYMONDH

JERSEYJOE wrote
YOU SHOULD HAVE 20+ AT IDLE WITH NEW PARTS.AND 55 TO 60 DRIVING DOWN THE ROAD. DID YOU REPLACE THE FRONT COVER? AMC'S WITH MILES TEND TO WEAR THE ALUMINUM COVER AND THE CLEARANCE BETWEEN THE OIL PUMP GEARS AND THE COVER EXCEED LIMITS. ALSO THE GEARS TEND TO EAT INTO THE OIL FILTER ADAPTER AND THE END CLEARANCE GOES SOUTH. THIS WILL APPEAR AS GOOD PRESSURE COLD AND LOW PRESSURE HOT.

EVERYTHING IS NEW , timing cover ,everything, i did forget to say the crank was turned 30 under but again its new head to toe.

JERSEYJOE

Remove the oil filter housing and check that the oil pump gears exceed the height of the casting by about .005-.007. The gasket thickness is about .010 new and about .085 compressed. This should leave you with about .001 to .002 gear to cover. Are you using a Bull Tear mid plate? You should consider it since the stock setup HAS steel gears riding on an aluminum surface. Just thinking out loud here. If all else is in order meaning rod and main clearances them the loss of hot oil pressure must be in the pumps area.. ANYONE???????

RAYMONDH

JERSEYJOE wrote
Remove the oil filter housing and check that the oil pump gears exceed the height of the casting by about .005-.007. The gasket thickness is about .010 new and about .085 compressed. This should leave you with about .001 to .002 gear to cover. Are you using a Bull Tear mid plate? You should consider it since the stock setup HAS steel gears riding on an aluminum surface.

Just thinking out loud here. If all else is in order meaning rod and main clearances them the loss of hot oil pressure must be in the pumps area..

ANYONE???????

I know for sure it is a stock setup ,but new. I am going to the machine shop in the morning to speak to the builder , he did mention he spent extra time on the clearence with gaskets and such.As for the mid plate im open for any solution. With only 100 miles i hope the bearings are in spec. thanks

hohner0006

I was always under the impression that as long as you had 5 - 10 psi at idle you won't hurt anything....but I understand your apprehension of that low of a psi on a new engine...I agree with jerseyjoe...look to your cover/gear clearances even though it is new as the tolerances can swing. Good luck..

JERSEYJOE

Yes they can. MC are you reading this?

MoPedal

JERSEYJOE wrote
Yes they can.

MC are you reading this?

He's got love on his mind and can't read! :lo1l:

jeepsr4ever

:?:

RAYMONDH

JERSEYJOE wrote
Yes they can.

MC are you reading this?

this mid plate will not increase pressure ? it will only help prevent wear on the lower plate correct ? , and the releif spring is only a issue if i had to much pressure correct? but are you saying maybe in this breif time that it ran t, he rotating pump may have worn just enough on the plate that it has dropped me the 10 psi that i am short? i

RAYMONDH

OK , I towed the car to the engine builder. I also gave him a 318**** part number with a 71 date stamped , oil filter adapter housing i found in the garage. and a couple springs . I also bought a 0.004 gasket.He ordered a new oil pump kit even though the NEW one in the car had 100 miles on it. He said they were at different dim. So he spent some time machining the propellers and with the thin gasket and the 37 year old housing ( since with the re pop the cavity for the spring and plunger was to loose ). With the engine cold i have 78 pounds ,cruising at 60 and at idle 22 , but touch the gas and it jumps to 60 , cam has a big lope. Im happy , thanks for all your help. 70 AMX back on the road.

RacerAMX

Please post the name and location of the builder. Its nice to know when someone does the right thing.