Specs for Mahle Euro S 90mm P/C
 

Does anyone have the specs for a Mahle Euro S 90mm piston and cylinder? (The ones with valve pockets and a unform dome - not a CIS dome). I'm planning to reuse a set of these on an engine I'm building and would like to check my measurements against the specs.

The compression ring clearances are all between 0.050 and 0.065mm. The cylinders are perfectly round (to my ability to measure) and 90.01mm in diameter. The pistons are 89.56mm in diameter (measured at the top) and 89.97mm measured at the skirt.

I don't have these numbers with me but they are in the dreaded Haynes manual and probably in other books as well. As a practical matter the things that matter are:

Ring lands less than .004 inches clearance to rings.
Original crosshashing on cylinders and no noticable "ridge" at top.
Piston running clearance is less than .004 inches.

Usually the pistons still have the machining grooves all the way around them. You can judge the wear by how much the grooves are worn off in areas like the skirt at the top and bottom (when the piston is sidways like in the engine).

I've never seen a set of worn out Nikasil cylinders. The pistons can show wear but it takes years and over 100k miles to see much wear on them.

-Andy

Thanks Andy. The pistons are well within these wear limits, so I cleaned them up, deglazed the cylinders with scotch-brite, and installed a new set of rings. Once I get the heads back, I'll stick them on the engine.