Need help with early 2.0 piston ID please
 

Hi folks, I'm mostly a lurker to this forum, but have recently torn down what has turned out to be an interesting engine. A German friend of mine says the piston pictured below is a 906 piston. I know from measurements that it's a 2L, but I intend on selling the set with the barrels and want to accurately represent them. A potential buyer says they are stock 2.0 S. What do you think?
http://forums.pelicanparts.com/uploa...1247786637.jpg
http://forums.pelicanparts.com/uploa...1247786653.jpg
http://forums.pelicanparts.com/uploa...1247786681.jpg
http://forums.pelicanparts.com/uploa...1247786758.jpg

The 906 and 1969 911S pistons are nearly identical. They look the same but I believe the compression ratio is just a little bit higher on the 906 pistons. The 906 pistons have a different part number for the 906E but maybe they were just a little lighter or inspected a little better.

You should search or ask your question here on the Early 911S Registry: http://www.early911sregistry.org/forum/index.php

There are many people there who are experts on early 911 details.

Here is the homepage: http://early911sregistry.org/

I know I have seen on there a part number list and photos comparings the 911S and 906.

here you go: http://www.early911sregistry.org/forum/showthread.php?t=26875&highlight=906+pistons

The 69S and the 906 pistons are nearly identical in appearance.

The 69S has the Mahle P/N 80P26E forged under the dome and the 906 has the P/N 80P26.

The other indicator is the inner bore of the cylinders. The 906 bores are not smooth and have "ridges" while the 69S bores are smooth.

Judging from the look of your cylinders, I 'll bet you'll find they are the 69S versions.

Also,

69S pistons measure 79.95mm for use with Birals

True 906 pistons measure 79.97mm for use with the Chromal/Nikasil cylinders