PeachParts Mercedes-Benz Forum - View Single Post

tcane · #5 01-09-2002, 01:03 PM

Larry:

Thanks for your comments. I kind of doubt the rings will be cast iron, also, given that the 21 to 1 compression ratio would be very rough on this type of ring. I have rebuilt a couple of other diesels and they had steel or ductile iron rings. Also, I do know that the vast majority of diesels have not used cast iron rings for many years.

The gray colored coating you mention to ID cast iron rings from others is a good one, however some ductile iron rings also have a grayish colored protective finish on them. As you probably know, cast iron rings are somewhat brittle and will break easily if twisted whereas ductile iron and steel rings can be twisted without breaking. But, who wants to take a chance of breaking a ring to find out what kind of metal it is made of when you can tap the ring and listen for a ringing/bell-like sound typical of ductile iron rings. Cast iron rings will make a dull sound when tapped.

I agree that you can use new cast iron rings without honing the cylinders, provided the cylinders are in good condition. I have successfully used cast iron rings without honing several times in the past, read tech articles in the past stating that honing is not needed if the cylinders are in good condition, and recently the same info about Ryder's overhaul procedures (it may have been a post by you).

I have mic'd and used plastigage where I could on all bearings and bearing surfaces in this engine. Everything is well within spec. and only two main bearings show a bit of taper (but within spec.). All bearings and related bearing surfaces are in very good condition with virtually no wear.

I ordered the parts yesterday and should get them next week. Have you ever tried the Benz Bin for M-B parts? They sell OEM M-B parts, have great prices, and their tech support is pretty good (Tom has a lot of experience with M-B's especially engines). I've used their parts several times and I am very satisfied with them. However, the Benz Bin does not have everything (who does except M-B), so I had to order some parts through another supplier. Check them out when you get the chance.

Good Luck with your 240 overhaul!

Tom