miracle cylinder scratch - Page 3 - PeachParts Mercedes-Benz Forum

ROLLGUY · #31 04-20-2012, 12:44 AM

With all the talk back and forth, has anyone else noticed that the original poster has not replied with any new information or comment? I for one would like to know if that is the factory engine, or has it been out of the car for rebuilding lately? Knowing this may help to figure out the best course of action for the OP.

snapped_bolt · #32 04-20-2012, 02:29 AM

Quote:

Originally Posted by Brian Carlton

See the piston at the bottom of the first photo????

My question was specifically directed to the OP (original poster).
I see. But I trust a machinist's square to aid in determining "parallel to piston travel".
Is there an exit wound in the side of the piston near the miracle scratch? Are there chew marks on the exhaust valve or seat? Does the scratch extend to the bottom of the cylinder?

I haven't seen definitive evidence to pin the blame on any individual yet.

I would have the sleeve replaced.

snapped_bolt

barry123400 · #33 04-20-2012, 09:02 AM

Quote:

Originally Posted by ROLLGUY

With all the talk back and forth, has anyone else noticed that the original poster has not replied with any new information or comment? I for one would like to know if that is the factory engine, or has it been out of the car for rebuilding lately? Knowing this may help to figure out the best course of action for the OP.

Probably a rebuilt. Quality control would have caught it on an original new or remanufactured engine if done by mercedes.

The real shame is that if a boring accident as suggested they would have just installed new sleeves. That was the time to efficiently correct the situation rather than reassemble the engine with the scratch in the liner.

gatorblue92 · #34 04-20-2012, 09:17 AM

Quote:

Originally Posted by nikkondy

My friend bought a 1987 300dt with low compression. He removed the cylinder head and sent it off to get resurfaced. He then purchased a victor reinz head gasket rebuilt kit with oil valve seals. He got the cylinder head back and reassembled it with all new gaskets. He tested the compression and all cylinder cylinders tested out to be 400. He then ran the engine for a bit. However he noticed that the victor reinz oil valve seals did not seal well and started to leak oil. He removed them and replaced them with original mercedes ones. As he was reassembling the head for the second time he noticed a hairline stratch on the fifth cylinder. Attached pictures show the stratch. The question is what could have caused this? Also, is this a major issue that he should be worried about and resurface the cylinder or just forget about it and reassemble.

So all cylinders tested at 400... I would run it as is and check the compression again.

bigblockchev · #35 04-20-2012, 10:32 AM

I vote boring bar. Slap it back together, test the compression and if it is not too bad run it until it smokes. Unfortunate but perhaps not fatal. Cheers Dan

funola · #36 04-20-2012, 10:43 AM

Quote:

Originally Posted by Beagle

That deep score mark was caused by the boring bar tool. The idiot machinist did not wind back the tool before lifting out the boring bar. The depth of the score mark is an indication of just how blunt the tool was and how far it was pushing the bar away. A properly sharpened tool would have scarcely left a mark at all even if he hadn't wound back! A score that deep is bad news as it allows hot gasses to escape that can eventually burn a vertical groove in the piston. SUE THEM!

When using a boring bar, isn't is done with at least 2 pass. i.e. run it down, then back up, so the boring bar is at the same position it started from while still spinning? If that was the case, no such score mark will occur.

We need more info from the OP.