Awkward oil PSI issue.

89_Red_Xr7

Registered User
Hola guys. It's been awhile since I've been around, but I've finally got my cat up and running again.
I've got a wierd oil pressure issue with the new engine, and wondering if anyone here has some insight/different POV?
On cold start, engine will go straight to 40Psi, and hold nicely. Once warmed, pressure will fluctuate between 20 and 0Psi:eek::confused: If the engine is fired cold and revved or allowed to warm and then revved, oil pressure will hit 50-55Psi at 2K rpm, and climb from there, hitting a max of around 70.

When the motor went together, bearings and oil pump were within spec according to Ford service manual. Engine was primed before initial firing, etc......

I'm just kinda at a loss as for what to do next. I know I can pull the K-member and check the bearings in about a day, but don't want to unless I absolutely have to.

Anyone else have any suggestions / input?

BTW, oil is 10-40 non-synthetic.

Thanks,
Andrew
 
That is bad oil pressure. If you don't check things out now you'll be fixing something later. With 10w40, if the bearings are all within spec you'd see 70-80psi cold (even at idle), which is the relief valve pressure in the pump, and then 65-75 hot above 2000rpm and hot idle would be about 40psi. You definitely have issues. Even my race motors that I set up on max clearance according to Ford specs still get more oil pressure than you are seeing so there is no way it's within specs.

On a new Ford engine you'd see about 80psi cold and 40-45psi hot idle even with 10w30 oil, and it should always run against the relief valve above 2500rpm regardless of engine temp.
 
oil pressure

I cant imagine spending all the money to rebuild an engine and not replacing the oil pump. That is where I would start. It is common for the drive gear in an oil pump to loosen and spin on the shaft causing low or erratic oil pressure.
 
I assume you have an actual gauge hooked up to it an are not going by the dash gauge or getting your figures from the oil pressure sending unit in any way?
 
Did you change the pressure relief spring and piston? Those things can hang up causing pre-mature pressure relief. When I change those I always debur them and the bore they run in so that everything moves nice and slick....
 
I switched out the spring and valve. I'll pull the pump and timing cover to check the operation on it. Anything to avoid dropping the pan!:eek:
 
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