I highly respect Jim. He is a hard working, honest and knowledgable MB guy, but you can see that I respectfully disagree with Jim about reusing pistons.

It is okay to bore the existing liners in a worn 616 or 617 engine and use oversize pistons. There is no need to go back to standard bore by replacing liners. I've done this a couple of times with great success.

Even if a diesel piston measures in spec., it is a HIGHLY stressed piece. I have in my box full of momentos a 616 piston with failed ring lands and it is not the only one that I've ever seen.

In many cases I'm sure that you can get by with used pistons, but you will have so much work and money in a rebuild, that for me it's just not worth the risk. Especially in a four cylinder where you only buy four pistons instead of five. Also I have seen pretty good prices on the early 616 pistons.

Jim, your neverending contribution to mshop is GREATLY appreciated.

Have a great day,

I consider myself lucky to have gotten a weight matched set of 5 Mahle pistons with rings for $675 about 2 years ago. I also changed the liners. Because I had to have the liners both bored and honed anyway, I suspect Larry was right in suggesting that new liners+std pistons was a waste of money vs. oversize pistons and bore and hone liners in place. However, I saw 1 thing during the liner replacement that gave me pause. The liner in #1 bore had very prominent carbon tracking on the OUTSIDE diameter of the liner. The only way I can figure that happened is the block/liner tolerance stackup combined with carbon buildup in the combustion chamber forced combustion gases through what must have been a pretty small gap. If the liner was bored any thinner, I wonder if it could present a problem.

Anyway, I think this is an area where there is no right answer. If the cost of pistons continues to rise quickly though, more pistons will end up being reused. I still think there's a market for a ring set that will fit pistons with reworked ring lands.

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Larry,

Just currious- are all your data points OM616 engines? My point being, the Turbo'd 617 engines have oil cooling jets which may greatly extend the piston life through better cooling of the piston.

Guess I'm lucky- all my engines right now have low hours, so rebuilding looks like a distant memory.

Michael

__________________
Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Yes indeed the 617 turbo engines do have the oil coolers but they are there for a reason, to help with the added stress and heat. To me that's a wash. In fact since the piston lives a tougher life in a turbo engine, I would be even more determined to replace them at overhaul time.

Pete,

The liners are plenty thick enough for overbore to the dimension of all available piston oversizes.

Have a great day,