8.5 or 9.8:1 Pistons?

[opticalfuel]

Here is a good test of everyone's technical knowledge of 911 SC pistons:

is this a 9.8:1 Piston or an 8.5:1?

I have an engine I am rebuilding for my 74 project. ( www.74911RS.com)
The engine may have been altered before I aquired it. Unknown.

These numbers are on the motor case: 930/09, SN:6393619 < this may be ironeous, since if it was modfied who knows what they did to it. I do know the prev owner said it drove very fast. It might indicate nothing at all. That is subjective.

The following is what my pistons look like (I can post more angles if needed, let me know and I will)



and:



See the other pictures posted on this subject for comparison:





So the discussion continues...

[otto in norway]

Those look very similar to the 9,8:1 mahle's I got last month.
I noticed that the "high spots" rise at a higher angle than my old 8,5:1 (Kolbeschmitt pistons). So you can easily see where the valves are going on the 9,8's...

[opticalfuel]

True... but how subtle is the difference between the two (8.5 and 9.8:1)? You can definitely see that there is a place where the valves 'go' on my pistons, but also... it looks like the hills or raised areas are more exaggerated on the pictures of the 9.8:1 pistons.

Is there any casting markings that tell you one way or another. I have one right here... what should I look for... there is a few things I can make out as far as numbers. Which ones' mean something (on the inside)

[otto in norway]

I don't know what to look for on the markings. But I am going to install my pistons this weekend, so I can take a few pictures of them, to compare if you like...
(I will try to get a got shot of the markings...)

[tom1394racing]

These are KS 9.8:1 CR Alusil SC pistons.

[otto in norway]

Yeah, I think you're right.
Posting some pics of my Mahle 9,8's for comparison: