oil pressure

[r lane]

Gentlemen, I have built dozens and dozens of street 911 motors over the years, and have just recently gotten involved in a couple of engines for a car that I am tracking. The first one went well enough, but #2 is a problem. The oil pressure was cold 3 bar max, tried diff senders and same. Oil pressure has never reared its head before, so put a Bosch mech gauge on the engine which said I had great pressure. Took car to the dyno, ran well had 265 HP at the wheels. Made 4-5 laps at Savanah and noticed 240 degrees oil temp and shut it down and had 260 degrees by the time I pitted. Part of that problem was a thrown belt which did not register at the alt light, but probably saved me a ventilated case as a slight intermittent wrap now emanated from of the engine. I burned the crank and 3 rods. Have rebuilt it and same oil pressure issue. Tested a sender and gauge out of another car which shows good pressure on the host car, but not on this new engine. The oil by pass bores and pistons seem fine, but I am hemorrhaging oil pressure some where. The blown motor had Clevite bearings on a 3.2 crank and this motor has GT3 bearings on a 3.0 crank. Would love to hear some constructive ideas and experience on this. Thanks, Bob

[dannobee]

How did the oil pump look? Did you take it apart and check the gears for any trash damage?

Oil pressure piston and spring look ok? Did you try shimming the spring to see if oil pressure comes up? Bearing clearances are within spec? And what do you mean by an intermittent wrap? Please clarify.

[r lane]

Forgot to mention the pump. It looked fine as well as I could assess it, but to cma, installed a new turbo pump. The by pass pistons came out cleanly, long spring and guide sleeve on the bottom one with the later plug that adds a little tension to the spring. Both cranks are used with the rod journals within .001 of standard and the mains as well. Wrap should have been rap i.e. rod knock. On a fresh motor, can't imagine needing to shim the by pass unless you are overlooking a systemic problem. Clearence on the mains about .003-.004 and the rods I have not checked as they were new Pauter and Carrillo.

[dannobee]

I asked about shimming for diagnostic purposes only, not to band-aid it.

Did you happen to check the thickness of the seals that seal the pressure side of the oil pump to the case?

[blue911rsr]

All your plugs in the crank all the brown seals in place? Was the case boat tailed are all the squirters in place . What case are you using?

[r lane]

Did not measure the seals at the oil pump. I am thinking you have two sizes for the pump and the cooler. One slightly larger than the other in diameter, but the same thickness. I think I have compared their thickness, but never put a mich on them. Plugs are in the crank, seals are in place on the pump. They are green, not brown. I did boat tail the case, but did not remove the squirters. Can't recall checking them other that running fluid and air though the case galleries. An 85 3.2 case. I drained the oil to see if I had a restriction from the tank to the pump, is OK. What is odd is I installed 9 qrts, but only 4 drained out. engine didn't run long enough to open the t'stat. Didn't think a dry motor would retain 5 qrts.

[bpu699]

Originally Posted by r lane

Gentlemen, I have built dozens and dozens of street 911 motors over the years, and have just recently gotten involved in a couple of engines for a car that I am tracking. The first one went well enough, but #2 is a problem. The oil pressure was cold 3 bar max, tried diff senders and same. Oil pressure has never reared its head before, so put a Bosch mech gauge on the engine which said I had great pressure. Took car to the dyno, ran well had 265 HP at the wheels. Made 4-5 laps at Savanah and noticed 240 degrees oil temp and shut it down and had 260 degrees by the time I pitted. Part of that problem was a thrown belt which did not register at the alt light, but probably saved me a ventilated case as a slight intermittent wrap now emanated from of the engine. I burned the crank and 3 rods. Have rebuilt it and same oil pressure issue. Tested a sender and gauge out of another car which shows good pressure on the host car, but not on this new engine. The oil by pass bores and pistons seem fine, but I am hemorrhaging oil pressure some where. The blown motor had Clevite bearings on a 3.2 crank and this motor has GT3 bearings on a 3.0 crank. Would love to hear some constructive ideas and experience on this. Thanks, Bob

Ever look on the supply side? Blocked line? Something in the oil tank blocking flow?

My 930 reached a max oil pressure of 4 bar hot before rebuild. That’s normal, but on the lower end. Rebuilding it due to some cam issues and lower leakdown on one cylinder or so.

I was expecting to find something when I tore the motor down. Nothing. Bearings looked good, everything mic’d out good. Oil pump looked good. Couldn’t find any reason for less than stellar pressure...

On the upside, 4 bar was plenty for track use, with no issues.

Rebuilding, will see what happens

I plan to check the oil tank, etc...

[Tippy]

Did you use Victor-Reinz gaskets on the low end?

I know TurboKraft stated they built an engine with VR gaskets and the engine had no oil pressure. Come to find out the square-faced O-rings between the cases were too short causing oil pump cavitation.

[Walt Fricke]

I've wondered about the effect of rod side clearance on oil pressure. You want flow for cooling, but too much (from wear on the crank radius?)could affect pressure?

[dannobee]

We ran piston guided rods in nascar (when legal) and the rod side clearance was north of 1/8". I don't think that's the problem.

[Walt Fricke]

Good to know, as I've not paid much attention to that.

[r lane]

Flushed the oil tank with solvent and it came gushing out of the line going to the pump. also pulled the line off the tank so I could look into the tank. Don't think I have a delivery problem from the tank. I have reinstalled the 4 qrts that I drained out and added 5 more. I used a different oil filter on this engine, so am going back to the OC54. Will install restrictors in the cam line spigots at the banjo. I don't think any of this is going to correct my problem, but you gotta try a few ridiculous measures before she comes back out and apart. the possibility of seals at the pump not doing their job. Piston squirters hemmorhging . Going to be a mind numbing endeavor.

[stownsen914]

Originally Posted by r lane

What is odd is I installed 9 qrts, but only 4 drained out. engine didn't run long enough to open the t'stat. Didn't think a dry motor would retain 5 qrts.

Something is seriously amiss there. That was engine + tank? Not clear if that is the result or the cause of your problem, but I have to believe it’s related.

[stownsen914]

Also, did you look at the oil filter?

[r lane]

After I watch my Auburn Tigers thump the Aggies tomorrow down in Texas, I plan to come down and finish my last gasp on this motor, before administering last rights, and begin the redo. Fingers are crossed though and will pass on the results. As the character in the movie, Deep Water Horizon, or what ever the name about the BP snafu, ''hope is not a tactic'' . War Eagle!

[dannobee]

One more thing. Does the car have a front oil cooler? Did you clean out the lines and replace the cooler(s) or clean the trombone? Since 911's have the goofy oil flow of coolers on the scavenge output, any engine bearing trash exits the engine and goes right into the coolers, lines and thermostat, unfiltered. If you didn't clean all of those out, that trash stays in there to do damage to your new engine.

It was an easy decision on our race cars. We'd simply toss all of the stuff on the scavenge side and replace it with new (but then again, we budgeted for that).

And if you're still running the engine mounted oil cooler, it needs to be replaced too, since there was previous bearing damage. There is no effective way to clean out all of the bearing trash.

[bpu699]

Originally Posted by r lane

Flushed the oil tank with solvent and it came gushing out of the line going to the pump. also pulled the line off the tank so I could look into the tank. Don't think I have a delivery problem from the tank. I have reinstalled the 4 qrts that I drained out and added 5 more. I used a different oil filter on this engine, so am going back to the OC54. Will install restrictors in the cam line spigots at the banjo. I don't think any of this is going to correct my problem, but you gotta try a few ridiculous measures before she comes back out and apart. the possibility of seals at the pump not doing their job. Piston squirters hemmorhging . Going to be a mind numbing endeavor.

I fo wonder how much oil pressure a squirted that’s stuck open bleeds off... mine had 3 stuck open... but then I keep hearing about all this excess pressure the pumps are designed to generate too...

Before you totally disassemble, consider the following hail mary’s though not sure it’s helpful
?

Hard shim both reliefs springs so they have no give... could be screwy relief piston...

Look into the oil tank while it running to verify not a supply problem, though that can get messy... oil tank should always be full if scavenge side is good...

Maybe check the oil pressure at a different location???

[bpu699]

Originally Posted by dannobee

One more thing. Does the car have a front oil cooler? Did you clean out the lines and replace the cooler(s) or clean the trombone? Since 911's have the goofy oil flow of coolers on the scavenge output, any engine bearing trash exits the engine and goes right into the coolers, lines and thermostat, unfiltered. If you didn't clean all of those out, that trash stays in there to do damage to your new engine.

It was an easy decision on our race cars. We'd simply toss all of the stuff on the scavenge side and replace it with new (but then again, we budgeted for that).

And if you're still running the engine mounted oil cooler, it needs to be replaced too, since there was previous bearing damage. There is no effective way to clean out all of the bearing trash.

Doesn’t the front cooler output dump through the oil filter? Hmmm... been a while since i looked at the schematics...

[dannobee]

Originally Posted by bpu699

Doesn’t the front cooler output dump through the oil filter? Hmmm... been a while since i looked at the schematics...

The filter is a bypass type. Factory spec is 1.0 bar. If the oil is cold, it's gonna be bypassing.

[Catorce]

This time upon rebuild bolt the case together without bearings and take a main bore measurement.