964 piston measurement spec?
 

OK guys, I can't find this info from in my printed in 1991 manuals and my friends with 964 spec books say it isn't in their spec books (printed in '93).

My factory manual says the 964 piston diameter should be measured 15mm from the bottom of the skirt. When I compared a 1990 piston to a later style (cylinder has sealing ring on top) I found that the skirt on the later style is longer.

For a later style 964 piston, how far up from the bottom should the piston diameter be measured?

thanks,
Chris

EDIT: It turns out that I have 993 pistons not 964 ones. Sooo... what I really need is the measurement spec for 993 pistons. Anyone have a 993 spec book?

Does this help?
http://forums.pelicanparts.com/uploa...1094215590.jpg

Thanks Bill, that's looks like what I have already but I appreciate the effort. Mine was printed in 1991, is your source newer?

I believe there were at least 3 different "flavors" of normal 964 pistons.

1) The factory manual mentions pre-mid 1990 pistons that lack the grove in the ring land between the top and middle rings.
2) The pistons found in the '91 motor I have
3) The pistons found in the late style P&C (cylidners with sealing ring) that have a shorter skirt but are otherwise similar to the #2

Here is picture of #2 on the left and #3 on the right that shows the height difference:
http://forums.pelicanparts.com/uploa...1094217528.jpg

The height difference comes from the skirt. You can see it better in this picture:

http://forums.pelicanparts.com/uploa...1094217613.jpg

It's probably a moot point but I don't like to take anything for granted.
-Chris

Aha! I tried to install rings on my "964" pistons last night and they turned out to be 993 pistons judging by the ring thickness. Sooo... what I really need is the measurement spec for 993 pistons. Anyone have a 993 spec book?
-Chris

Chris, you do know that 993 pistons are not compatible w/ 964 rods?

Anyhoo, does this help?


http://forums.pelicanparts.com/uploa...1095461320.jpg

http://forums.pelicanparts.com/uploa...1095461340.jpg

Aaaaagh!

Nooooooo (camera pans back as Chris screams at sky).

I bought what were supposed to be 964 P&C but they turned out to be 993's so I have some rings being sent 2 day air to fit pistons that won't work with my motor. Sigh. At least I bought them from a reputable guy so I should be able to get my money back.

As always Bill, Thanks.

-Chris