Cylinders and Pistons diameter size
 

Hi,

I'm newby on this forum, and American is not my native language. I'll do my best to be understandable.

My Euro Carrera 2,7 engine is being rebuilt.

For reliability concern, and also to make my car 100% original, I'm replacing high compression Pistons by standard ones

I found a set of nice original pistons. But one is missing.

My concern is diameter tolerance group.

Cylinders are group 0 (90 to 90,01mm)
Pistons are group 1 (89,955 to 89,965)

Tolerance group are 0,01mm stepped. It's not a lot, regarding the 0,15mm running clearance.

My questions are:

1. The max running clearance is 0,15mm. What about the minimum clearance?

2 Is it acceptable to mix a group 0 cylinder with a group 1 piston, or a group 1 cylinder with a group 0 piston, provided that the running clearance is within the limits?

3. Are the new MAHLE Pistons compatible with old cylinders? On MAHLE data sheet, they only give the nominal diameter, with no tolerance info. Also, I guess the weight could be different, as material may have differed during the years.

I know that an answer could be: replace all by new. But.... Money is also a concern.

Thanks for help

Dan

Pistons
 

You not only need to have pistons in the same diameter group, but they should also weigh the same. Otherwise, you will be introducing an imbalance into your newly rebuilt engine!