tall02

Dear fellow members

I am rebuilding my 92 Porsche 964 engine 3.6L and I wish to check my piston to cylinder tolerance and my piston ring gap tolerance. Can anyone direct me to where I can find these allowable tolerances?

Any help would be appreciated

Geoffrey

The specifications are in the factory service manuals and the factory technical specification book. They will be dependant on both the cylinder height tolerance group (5 or 6) and the bore tolerance group (0 - 4). If you post back the numbers on the cylinders, I can look them up for you. The bore is measured 56mm from the top of the cylinder.

I have not found the piston ring gap listed in any of the manuals, so when blueprinting the engines, I use my own specification.

tall02

Dear Geoffrey

Thanks for the response. The markings on the cylinder are as follows:

Mahle US A
95ZN6 ++++ A 2 W6



The only one that is stamped in is the #2. The rest are raised-cast into the cylinder.

Thanks

tall02

Dear Geoffrey

I cleaned the cylinders and also found a 5 in a triangle with a #1 next to it outside the triangle.

Geoffrey

Ok, so you have a cylinder height group of 5 and a bore tolerance group of 1

measurements in mm
Height = 82.750 with a -.020 allowance
Cylinder bore = 100.007 with a +.007 tolerance