Engine Rebuild Block questions - Cylinder Inserts?

[roman.lysiak]

Hello fellow Faq-ers,

 

I'm in the midst of a 72tii engine tear down to replace my worn 73tii version. Its a bummer that the block numbers won't match the chassis anymore, but having a spare tii engine allows me to have a reduced downtime, when swapping the old one out. Presently I've stripped everything apart and have taken the block, pistons, crank, to the machinist to assess what is to spec and what needs machining. Cylinder 2 was seized so the rust and scoring on this cylinder are forcing me to get new pistons 90mm. Looking to purchase the Mahle ones from IE.

 

My question is, did these blocks use cylinder inserts which could be replaced and bored so that I could possibly reuse the old pistons and save spending the $800USD on a new set?

 

Thanks

 

Roman

[Ensign]

There was a recent thread discussing sleeves:

 

 

[bergie33]

No sleeves in the original blocks. If you want to use the old pistons, first make sure they are in good shape and correct specs. Then, they can bore the block and insert sleeves to the size of your old pistons. You might find the difference in cost is not as much as you think.

[Son of Marty]

As Karl said be sure to have your pistons checked especially around the ring lands to be sure they will work, many, if not most high mileage m10 pistons fail this test. 

[roman.lysiak]

Got it. Ya, it was a question of cost, but I need to check the condition of the cylinders and the ring land condition to see if its even worth going that route. Will see if I can post some pics soon. And thank you for the link to the search. I tried searching " cylinder inserts" and nothing came up. Not sure why.

 

Roman

[Conserv]

8 minutes ago, roman.lysiak said:

… I tried searching " cylinder inserts" and nothing came up. Not sure why…

 

Roman,

 

The term used with most engines, such as the BMW M10, is sleeving, as Ensign and bergie33 referred to above. The “inserts” are “sleeves”, and the original block is drilled out and a sleeve fitted.

 

Regards,

 

Steve

 

 

[Son of Marty]

Yes, the sleeve is cryogenically chilled and the block is heated, after the sleeve warms and the block cooled they are mated for life.

[Conserv]

Roman,

 

I couldn’t quite tell which engine — ‘72 or ‘73 — has the cylinder 2 issue. It sounds like you own a 1973 tii and are transplanting a 1972 tii engine into it. Is that correct? If so, are you giving up on the original numbers-matching engine (a.) because it has serious issues, or (b.) simply to reduce the car’s downtime — I’m guessing the car must be a daily driver?

 

If you read the recent thread, linked above by @Ensign, you may decide you don’t need to bore all four cylinders to 90 mm.; you could sleeve one cylinder instead. Or you could sleeve all four and return to standard bore, first oversize, second oversize, etc. — based on what pistons you find. Of course, returning all four cylinders to standard size does not guarantee you can re-use original standard-size pistons. As @Son of Marty says above, being able to re-use original standard size pistons is a reach on most 50-year-old M10 engines.

 

If you were not dealing with round taillight tii’s, a matching number engine would probably be far less critical. But you appear to be restoring or maintaining a round taillight tii.

 

Regards,

 

Steve

 

[jimk]

13 hours ago, roman.lysiak said:

Cylinder 2 was seized so the rust and scoring on this cylinder are forcing me to get new pistons 90mm.

Pits from rusting run deep in cast iron.  Boring often won't get to sound cylinder material.

13 hours ago, roman.lysiak said:

My question is, did these blocks use cylinder inserts which could be replaced and bored so that I could possibly reuse the old pistons

Boring to fit a sleeve can distort the two adjoining cylinders such that those other two will need to go oversize, the original pistons then can't be reused.

 

Try to bore first cyl 2 to see if the pits are removed cleanly without a sleeve.  Do not bore the other 3 yet until the decision on course of action to cyl 2 is made.  Boring to set a sleeve should be done before any adjacent cylinders are worked because they can be distorted after the cyl 2 sleeve is set.  Then bore/finish all 4 cyclinders to the pistons you select.

 

Been there.

 

Just a reminder, the other post with pics show a 121 head, so bathtub pistons will be needed.

Edited January 25, 2022 by jimk