[L8apex32]

1981 911SC Euro, used for PCA e-stock racing only

I bought the car knowing it had leak down problems on the #1 cylinder. It burned some oil, maybe a quart or 1.5 quarts in a weekend. I drove it this way for 2 years.

In Apr of 2011, I had my engine rebuilt by a reputable shop. They found that the #1 cylinder had broken cylinder rings. And, that I was lucky that they stayed in the ring grooves. No damage to any of the cylinders was done.

During the rebuild, we opened the case and replaced the crank bearings. It was a pretty decent rebuild, but did not include new pistons or cylinders.

After the rebuild, it smoked as much as or more than before. But, it ran much more smoothly. It seemed to be more powerful, but we didn't dyno it. The builder said the smoke was because it was built a little looser than a new engine and should have more power because of this.

During the 2nd race weekend, I thought I saw some smoke coming out the exhaust after certain corners.

For the 3rd weekend, there was a LOT of smoke coming out and, sometimes, the engine would run really badly due to burning too much oil. The problem got so bad that oil came out the oil cap. This lead me to believe that I had another case of cylinder pressure blowing by the rings. I had to abandon that race weekend.

At home, I did a leak down and found that cylinders 1, 2 and 3 all have a major problem. One is 20%, one 30% and one 50% leak down. Cylinders 4, 5 and 6 are all great, better than any of the 6 were pre-rebuild - with less than 5% leak down.

I am fully convinced of major blow by for 2 big reasons. One, oil came out the oil cap. And for two, during the leak down, I could hear oil burbling in the case.

My engine builder and I are working out the details of how to proceed, but nothing further has been done yet.

My question is, what can cause 3 cylinders to have ring problems after just a few weekends, but NOT the other 3 cylinders? My engine builder assumes that something other than the rebuild is causing this - perhaps running lean or something. He of course wants to fix this, but charge me more if everything he did was done correctly the first time.

My thought is that there is nothing that can cause 3 cylinders rings to break in less than 3 weekend and that after a rebuild, the engine should not smoke to begin with. Am I right to assume that the rebuild is the problem?

Also, what can cause rings to break in any case? These should be brand new rings in a fresh rebuild.

Any thoughts would be great.
Thanks.