Update with test results
http://forums.pelicanparts.com/uploa...1546895685.JPG

Maybe the experts will disagree, but in my mind the 15% exhaust is not your problem. I had a similar leakdown result due to carbon coming loose on the removal of the plug and getting on the exhaust valve.

Maybe not the source of the oil, but it certainly seems too much for a new engine build. OP, who did the heads? If I saw that result on a new engine I would, at a minimum, check the valve lash for that cylinder.

I think the one exhaust leak will be gone when I adjust the valves.
Can't really call this a new rebuild anymore as I've put around 8,000 km on it and it has been mostly track time.

I had two (!) missing valve guide seals. And the oil consumption was tremendous.

Carbon build up caused the valves to stick open due to chunks between the valve and seats.

Drove the car for only 1 month and added 3 quarts!

Pull it apart, rebuild the heads myself. Had to lap the valves and carve the carbon off the head and ports

What a pita

I assume this was very obvious when you did a leak down test?

The stuck exhaust valve leaked air. Yes

The cause of the leak was carbon build up

The cause of carbon was oil leaking from the seal

The oil leak was from missing valve guide seal.

I learned that there are many ways to screw up my engine. And the steep learning curve was personally confidence draining. 2015 had four top ends.

But it was not obvious the oil seal was missing

I only found the missing seals because the “race springs” caused so much premature rocker wear.

I really can’t remember why I tore down the cam tower which lead to the rocker shaft wear discovery.

While trying to remove the stiff “race” springs I had to go a friend with a string enough spring compressor.

That is when he noticed the missing seal because the valve just fell out of the head.

That was a shock. Found (2) of (12) missing.

My point of my tale of woe is: when chasing down these problems, be observant of other parts that could cause a similar issue and make sure there aren’t two or more causes happening at the same time.

Thinking out loud here.
I noticed a whistle sound under throttle. Now that it is cold out it doesn't start as well as it should.
Could a vacuum leak be the culprit to oil usage?

I am guessing you are refferring to this post? http://forums.pelicanparts.com/porsche-911-technical-forum/1016249-1988-carerra-smoke-idle.html

My engine builder said they didnt recommend my request during rebuild of my 3.2 to 3.4 as the risk of what you have described was too high. Something about the materials used when recoating. I had the alusil not the nikasil. So i bit the bullet and bought new Mahle 3.2 P&Cs.

In CA with our SMOG inspections every two years I couldnt take the risk.

Not a performance issue just a smog issue as I was told.

Getting the rings to seat on JE pistons and nikasil on alusil cylinders is a bear and requires a light hone, not the deep stuff

Also, generally speaking, the je pistons run much looser in the cylinders than stock. The upper diameter was about 1mm smaller than the bore, compared to ~0.5mm smaller for the stock KS piston.

I think the floppy fit constributes to poor sealing when cold, and extended break in time.

Mahle and KS stock P&C are superior. The cost difference unfortunately is staggering.

Hence a strong market for JE and plated alusil cylinders. And the extended break in.

Great post vfr750. Agree on all points.

One could run just iron liners with JE pistons and those rings will seat just fine. Running for cover now

Yea, it is a shame that Mahle, who makes forged pistons for CHEYs, doesn't make a forged replacement piston for 95mm cylinders. Oh well.

Yes, it seemed like my JE piston rings took for ever to seal in my used Mahle cylinders, but all is good now. A friend of mine has an SC motor with re-plated cylinders and CP pistons. I noticed he had quite a bit of smoke coming from his oil tank the other day.

Yes Sir.


I wish my builder told me this.



Hopefully forever is more than the 5,000 km I've put on after the rebuild.

I don't remember exactly, but IIRC it was between 1 and 2K miles. That included a few auto crosses and a track day.

1/2 of my mileage is to and from the track and the other 1/2 is on the track.
My engine builder suggested having my oil level just at the end of the dipstick to see if it helps.
Sort of hard to monitor it that way though.

911 Rod

Yes, I hear ya.

I was torn as many on RL and Pelican have done the 3.2 to 3.4 hone and coat with good results. But as my builder said its not guaranteed as we have seen, even with good builders.

If I wasnt in CA I might have taken the risk. But with our stringent SMOG requirements I went the safer route.

You might double check with replies on this thread, but my limited understanding from my builder is worse case is oil consumption up a little, smoke on start up but no power or performance loss.

Sorry this happened but good to share your experience so others can make informed future decisions.

Lucky it makes lots of power!
I'm concerned if I try and do a rebuild I will get the same results.

Refer back to post #8. There was another recent similar thread. Poster, IIRC, had to have cylinders re-honed to fix problem.

FWIW. If you search here there are a couple of old threads discussing the cylinder wall finish to ring seating issue. With Nicasils the wall finish is critical to seating and sealing.

I was cleaning out my email and I made a note to read this and respond. Slipped my mind to respond with my question.......

What baffles me here is how the Millennium Technologies cylinder plating could be honed wrong. Reason I say that is LN Engineering uses Millennium to plate their Nickies cylinders and they use the same JE pistons (or CP, or Mahle) that we would choose to use in our old cylinders. So the honing spec on the Nickies plating should be the same as the re-plating of the old cylinders, since both would be using the same JE piston rings.