Crankcase Pressure fluctuations?

[teveo]

Hi, I am back to tuning my fresh Supertec 2.7RS engine. This engine went into my carrera 74 last year or so. I have only done 15-20 miles on it, mostly for tuning the MFI.

Problem: every 2 or 3 times car is left for some time the case seem to fill up.

I have read that this can happen. Car will smoke on startup and for a short while, when I reach operation temperature it will start leaking(squeezing out oil) from the left side valve cover, that may only be the gasket and I am installing new silicone gaskets there.

Having read a few of the crankcase pressure threads I decided to verify that engine is free of shop towels or debris and take it from there.

So far I drained it and checked the sump, the sump and what I can see is very clean so nothing left in there.
I decided to verify that the crank ventilation is free and it works fine, it is "pumping air" so that seems fine, the ventilation tube from the oil tank into the air filter is also free breathing.

I am now checking the scavenge side and taking apart the left heat exchanger to get a better look at everything.
Based on the diagrams I can find, the pressure should not be related to the oil thermostat but I will take it out and check.

Anyone have something to add to my checklist?
- check sump - ok clean
- check the breather hoses and test for small pressure/pumping under idle - ok
- destroy and inspect the oil filter
- check the thermostat
- check the scavenge tube from pump to oil tank and related hoses.
- "fish around" in the bottom of oil tank ( for potential debris )
- "seal" the mfi pump from the engine oil ( how many ml or cl is recommended? top it up to the upper hose?)

I am running BradPenn 20w50 green oil but consider swapping to mobile1, any thoughts?

[lindy 911]

There should be zero crank-case pressure. The "vent" on top of the motor where the breather hose connects is a direct shot to the interior of the case and is large. My motor (3.0 SC) will fill the case with oil after a couple of days sitting. This happens by way of the feed oil line from the tank and the tank itself being higher than the oil pump. Gravity will force the oil past the pump gears and out the scavenge pick-up into the case.

I think this is normal with all air-cooled Porsches and after start-up the oil is quickly scavenged from the case to the tank. You can watch the gauge on the dash go from low to full in a matter of a minute or so of just above idle running. The start up smoke is oil getting into the bottom of the cylinders and soaking past the rings. Initial start-up burns this oil quickly; not pretty but it's part of owning one of these cars.

The leak you describe is also pretty common if all isn't correct with the valve cover. Did you have them off since you got the motor from Henry? If so, I think he uses the gasket with a silicone bead for sealing and they are top notch. I would check the gasket and the cover for proper installation and nut torque. Too tight and the cover will leak all over the place. Also, give Henry a shout about the oil leak back issue, I think you'll find it's perfectly normal.

I think the easiest solution to the smoke problem is to drive your car more often.

Lindy

[teveo]

Yes, I really hope the pressure is more or less zero, but the case breather does indeed pump alot of air as everything heats up. I also read that the pressure can be more than normal when rings are not seated yet. In my case that is very possible due to the little use.

As I got the car up in the lift I found that I need to replace sway bar bushings, the car will be in the lift until I get the parts so I will go through the scavenge system and also connect my front oil cooler again, will take out the external mocal thermostat and clean it before I hook it up.

Oil pressure is fine and never fluctuate, the most important issue for me was to check out that there is no debris in crank ventilation or oil circulation. I will use the silicone style valve-cover gaskets and torque them exactly as specified.

[Steve@Rennsport]

Do a leakdown test to make sure the rings have completely seated before you do anything.

[teveo]

Well, I got the exhaust off and both valve covers. Big surprise on the left bank, I guess you can see a problem here. .. it is not the taped up sump hole!



Right side ... all well.


Any thoughts? I have had good oil pressure all time so even if the shaft did not seal it should not have created a big problem (I hope).
I have to check on a spare head to see exactly how the oil circulate in head but this is pressure side so it may have sprayed alot of oil here.

I would perhaps lead to the oil from tank leaking into case faster than "normal" as the oil could bypass the shafts with less resistance.


Cylinder 1's shaft is approx 3-4 mm out of its house else position is ok.

[Eagledriver]

Yes, that is your leak source. Check the other side as well. Need to torque those bolts very tight.

-Andy

[Flat6pac]

The rocker shaft is suposed to be above flush on the thin boss side. Your #3 exhaustis moved to the left too much, you want it above flush.\Bruce

[lindy 911]

What is the leak source? I'm not seeing anything from the photos posted. Are you saying the rocker shafts are leaking? I can't see that in the photos. Are you saying the return tubes are leaking? I can't see that either. Torque what bolts very tight? What am I missing?

Lindy

[lindy 911]

The only pressure in the top end is to the cam spray bar. The rockers and shafts are splash lubed so no pressure there. If the rocker shafts were installed this way from the builder, Henry has some "splain'n" to do...

[teveo]

Shaft bolts were all loose, shaking around in the head, they came out with the valve cover .. no wrenching neccessary.

Look at the wet valve cover, all sections should not be wet with oil. Number 1 and number 3 rockers shafts are spitting oil straight out of engine.



I will align all rocker shafts flush with the thin edge and tighten to required torque, anyone recommend thread lock there?

[lindy 911]

I did not realize those were the shaft bolts in the valve cover; wow. Oh Henry?

[teveo]

Last year when I contacted Supertec about the leaks I had (from valve covers) Henry advised me to check the rocker shafts. Had I lived in CA I think Supertec would have fixed this for free.

I never got around to debug as I did not use the car, I have only covered some 10 miles after that. This must either have been a problem with the bolts or they have not been torqued down (sufficiently). I would vote for the second as right bank is all well.

There is no damage done, and this thing happen with 35 year old materials. To me the most important is to get my carrera running like it should and to be confident everything is up to grabs.

[lindy 911]

Your photos show assembly lube on the cam lobes. That tells me this motor has not run much at all. I think you have located your oil leak problem and solved it with the tightening of the rocker shafts. Back to your original post question about the case filling; it's time to drive this baby. The first step though is to do the cam break in at 2000 rpm for 20 minutes. Let the motor get good and warm so the hot oil melts and absorbs the assembly lube, then change the oil. Once that is accomplished, it's time to drive it for the first 500 miles, then check the valves for clearance.

The oil in the crank case will take care of itself with driving.

[racing97]

Probably wouldn't be a bad idea to leak it down as Steve suggested just to ease your mind. I am sure you would have ring seal by now and I would assume the builder ran it a bit before he gave it to you.

regards

[lindy 911]

Rings won't seal in the little time this motor has run. If you look at the photos the assembly lube is barely run off. I would treat it like a brand new motor (which it is) and break in the cams, change the oil and then go drive it. After that, do a leak down.

Lindy

[teveo]

Everything is hooked up and I have removed a few steps on the checklist, had to buy a 1/4" torque wrench to get to the shaft bolts.

It is a good addition to the toolkit, starting at 4nm it will be handy for various 6mm applications and of course valve covers as well. My 3/8" would not get into the cam housing and it starts too high for eg. the valve covers.

I am about to put mobil1 in her, 5W50 that is. I dont want to use the BradPenn 20W50 until I have run the initial 500 miles, will try to see if I can get a brake in additive locally if that is recommended.

I wanted to use a free flowing oil just because the bad stomach feeling (oil, pressure, damp and possible fire hazard) has not let go yet.

[mcfoo]

It would be nice if the person who built this motor would chime in, own up or man up.

Tom B.

[lindy 911]

I would not use Mobil 1 for the break in run. A good DINO with ZDDP adder is the ticket. It's not going to be in there long enough to matter what brand. GM makes a good additive as does Champion oil.

[356RS]

teveo,
How is the 2.7RS engine doing? Back together or have you been working on the 68R?

[Henry Schmidt]

Originally Posted by mcfoo

It would be nice if the person who built this motor would chime in, own up or man up.

Tom B.

I contacted Trond directly.