94mm cylinder wear limits...

[ecksrash]

I have a set of Mahle cylinders that have seen their share of abuse. What are the limits before they can no longer be honed and returned to service? Thanks DS

[Marc]

The conventional wisdom is that standard-sized rings can accommodate up to .010" cylinderwall taper - but that's asking a lot of them, I wouldn't expect more than ~20,000 miles' life, and it'll probably be a little noisy (especially when cold).
.004"-.005" taper is probably the most you could accept to make it worth your time to use them. No bore gauge? Put a ring in the cylinder and square it up just below the ring ridge near the top. Measure the end gap with feeler gauges. Repeat at an unworn spot on the cylinder (above the ring ridge if the carbon's been removed...down near the bottom of the bore will do also).

The difference in the ring gap measurements is roughly 3 times the taper wear, so if the difference is over ~.015" they're probably not worth messing with. You could have them tru-honed out to reduce the taper and then get the piston skirts knurled to reduce the side clearance, but unless you're getting a helluva deal on machinework that's money that should be put towards a new set.

[ecksrash]

Thanks Marc... Good info.

[PEPPE]

sorry what is the "skirt knurling"

[The Newf]

sorry what is the "skirt knurling"

Knurling is done with a tool that displaces & raises some of the skirt material to make it larger in overall diameter.It leaves a checkerboard pattern.Used on valve guides too.

[PEPPE]

ok i understand, i saw some of those tools to be used on lathes. it is like a radio knob with a pattern. thanks