How much oil pressure is too much?

[Pat S]

early 2.7L, I rebuilt the engine about 2K miles ago. Oil bypass mod with correct pistons, turbo restrictors for the cam lines.

I have the oil pressure gauge that reads 0,20,60,100,140. And I believe it to be correct, it worked well before I tore the engine down and seems to work correctly now.

When the engine is totally cold at 2K rpm I'll see 100psi. I try to keep it under that pressure reading. When warmed up at 180F-210F at readline I hit 60 or so psi. Initially I though it was high due to the oil being very cold in the winter, but I'm still seeing the high pressures at startup. The pressure levels seem right when the engine is warm.

So, is it possible to build too much pressure? I'm pretty sure it is primarily a result of the turbo cam oil line restrictors and the oil being so think when cold, but I'm not sure what the "right" pressure should be or where I need to be concerned. Can I run it all the way to 140psi (about 3000rpm when cold) or is even 100psi too much?

Pat

[dtw]

The cold pressure at 2k sounds just a touch high - but my fresh 2.4 is right in there at ~30 deg. temps. Now that we're in the 70s and 80s here in NC, cold pressures range from 40-60 at idle through 2k.

60 psi warm at redline sounds fine. If you continue to think you have higher pressure than you should, inspect both of your oil bypass pistons to ensure that they are not sticking shut in their bores. But I think your pressures sound fine, especially for April in Aurora.

[Doug Steinel]

Bruce Anderson's rule of thumb: Once warm, you should have at least 15 psi for every 1,000 rpm. I do not recall his ever saying anything about the pressure being too high... the opposite is usually the problem.

[aigel]

I would put a mechanical gauge on there and check it against your electronic one. The argument: "It worked well before, so it can't be broken" really doesn't work well. Things break, for no reason, and in your case, disturbing things often make things break much easier.

George

[MotoSook]

I wasn't aware that the oil by-pass mod. involved any changes to the relief circuit..such that the relief didn't work. If the readings are right, which they appear to be since the values are changing with the engine temp to a pressure that is expected, I would suspect that the pressure relief is not working. The springs on the oil pressure relief are designed for 80 psig or there abouts. Did you install the relief springs correctly?

[ischmitz]

My first thought would have been to say you can't have too much. But then I read Thom Fitzpatric's horror story where he blew out on of the rubber seals at the oil pump/case. As a result his pressure fed chain tensioner collapsed and the entire motor had to come apart to get to the rubber seal. The tensioner was busted, too. All because some dufus (PO) had installed a booster spring for the oil pressure relive valve.

I remember my 2.7 would go up to above 60 PSI at 2000 RPM and then suddenly the pressure needle would jerk down when cold. That was the oil pressure relive valve opening. Once warm I had the standard 15 PSI per 1000 up to 60 PSI. Maybe the pressure relive piston wasn't moving smooth with the engine cold.

Take the advice and use a mechanical gauge to see what's going on, if you are above 5 bar (80 PSI) you need to be concerned.

Ingo

[BURN-BROS]

I believe after 80 psi, the oil's ability to transfer heat starts to diminish.