Cylinder liners or overbore?

I gave up on finding my machinist with mucho MB experience. I guess he's gone to Disneyland. He's a one man shop and his phone has been ringing off the hook for a week and a half. I hope he's okay.

I know a reputable machine shop that can do the machine work competently, but I was looking to the other machinist for advice regarding replacing the liners or simply going to the next overbore. I would not reuse the pistons in either case.

Is there any valid reason to go the extra expense and replace the liners rather than over bore. The oversize is .5 millimeters, which I believe is only .020".

Any experiences in this area that you can share?

Thanks everyone,

[engatwork]

Larry
If it were mine and I could get the oversize pistons and rings and it only went up one oversize (or so) I would probably go with the overbore. I assume too, that the machine shop you have found has taken a close look at the existing liners and told you that you can get away with one or two oversizes and can give you a good bore. I have done it on a gasoline vehicle that was not a MB.
Jim

[MBJOE]

Larry
I guess you and I have a complete different opinion on this subject. After rebuilding several 240D's and three 300D's I have only bought a new set of pistons two times.
I have always considered the purchase of new pistons the most expensive part of rebuilding one of these engines. As long as the ring grooves and skirts are within the specs and the top of the piston is not pitted I reuse the old pistons.
The liners on the other hand are the one of the least expensive parts to buy. and since the liners have to be bored to fit the new pistons anyway, I just have them bored to fit the old pistons. This was always done after a careful inspection with a micrometer of the wearable points on the piston.
As far as your mechanic goes , I gave up a good while ago on finding one that has done the correct amount of reading and study with these engines. Most of the time most of them can't even convert the metric measurements of the MB service manual to SAE or back again.

My stable
83 300D 156000
81 240D 333000 +
75 300D 162000

MBJoe,

Thanks for the reply.

No, I don't think that we disagree at all. Had the pistons been in good shape, I would certainly have considered liners, and bore to fit the original pistons. However, a ring land was broken on one piston, I didn't like the looks of the skirt on another.

I have this engine stripped to the bare block and took it to a machinist who knows his stuff and can convert mm to inches in his sleep. The only shortcoming he has is little experience with these particular engines. The other machinist has done beaucoup MB diesels and I was looking forward to his advice and experience with the breed.

The machinist has much automotive machining experience and a "do it right" attitude, so I think we will get it all worked out okay in the end. In my way of thinking, "attitude is everything".

Have a great day,

The cylinders are cleaning up at .020. The oversize pistons are being delivered to the machine shop today. I will clean parts and engine compartment this weekend, get the block and pistons back next week and start putting everything back together next weekend.

Have a nice weekend,

[MBJOE]

Larry ,
If you don't mind me asking. How much did you have to part with for those new oversize pistons.

Pistons were $145 each with pins and rings.

Have a great weekend,