karl ruiter

I stripped my old motor down last night and on about 1/2 the cylinders the oil (bottom) ring broke as it came out of the cylinder. I don't mind about that, but I have a factory new block with pistons and rings already installed that will be the basis of my new motor. I have to pull the pistons out for the new block to install the rods and really do not want to break the brand new rings.

So...I'm looking for tricks before I pull the new pistons. It may not be a problem as there is no ridge on the new block, but then there was not much of one on the old block either. I suppose I could try pull it out to the point that the oil ring was about 1/2 way exposed and get the ring compresser on it, but it seems pretty tricky to get it that exact.

GregBBRD

It will not be an issue. Just push them out. For the old engine, try removing the carbon ring, first.

largecar379

you can get an upper cylinder cutting tool from most auto parts stores, for cutting the carbon off and cutting the transition from worn cylinder to non-worn area near the top deck (under the carbon).

this will prevent the ring from catching on the carbon and cylinder wear area and breaking the rings as they and the pistons are pushed up out of the cylinders.

of the 928 blocks that I have seen so far, upper cylinder wear doesn't compare with like mileage iron blocks. the 928 blocks have little or no wear compared to the iron blocks I have worked on over the years.



--Russ

karl ruiter

Thanks guys. Out they come.

Lizard928

Karl,

I would not recommend the tool Russ is suggesting on our alusil engines! If you do you will need to rehone the bores with the felt pads and special paste.

atb

Agreed, a ridge reamer may cause some issues.

123quattro

I would also say that ridge reamers can be the devil. I used one on an iron block Audi engine to try and save the rings. Well, the pistons came right out, but the reamer belled out the top of the block so then I had to bore it and have custom pistons made since there is no factory oversize stuff. I ended up spending $2000 to save a $100 set of rings.

Mike Frye

Yeah, but you got a bored out engine with larger displacement out of it.

largecar379

the ridge reamer would only cut the area the area rings do not travel on.


renewing this area with pads and paste is unnecessary.

as I said, the 928 blocks that I have seen/worked on do not have enough of a ridge to be concerned with to warrant using a ridge reamer, compared to a similar mileage iron block.

I have disassembled 11 so far, from 4.5L to 5.0L, and only one block (the 4.5L that came out of my 80 Euro) had broken rings with broken pistons. There was no ridge and little carbon build up in this particular block.

your experience may be much different.

karl ruiter

Thanks guys. I think I agree with Russ here, since the carboned up area does not see any contact with rings , although I am generally very paranoid about anything at all touching the alumisil walls. In any case the block I am working on now is 100% extra virgin, factory new, so I am going to follow Greg's advice (generally a good idea, I think) and just pull 'em out.

RyanPerrella

if your breaking rings pulling out pistons out of an M28, your doing something wrong.

123quattro

Uh, yeah. I picked up 0.07 liter for 2k. What a deal. I do have some fancy Diamond Racing pistons now though.
The reamer I used not only removed the carbon deposit, but it also removed block material. Once it started cutting it kept expanding as it screwed up out of the bore. Granted I used a crappy spring loaded cutting tool version. I would just be very careful with one.

karl ruiter

Ryan-That's why I asked. But, the oil rings on this particular motor were super brittle. I wiped out the bores and removed most of the carbon with solvent, checked for ridges, and pushed out the pistons with one or two fingers of pressure. It could be that the rings were already broken. After all-I took the motor down because it was smoking, but I would guess that broken oil rings would have scored up the cylinder walls, which I generally did not see.
John-So if I were to do this again it sound like a reamer would be a risky option. I wonder what the best chemical approach to removing the carbon would be? I used cleaning solvent and it seemed to take off most of it.

blown 87

One thing I do not understand is that the oil control ring is a three part deal and not very brittle, it looks like that one of the compression rings would have broken first.

Lizard928

They were most likely already broken.