Help on deciding to resleeve a block

[Shonick]

I have an original numbers matching engine in a 1969 BMW 2002. Evidently the engine has been bored at least once before. I am not sure if there the machinist can overbore anymore. I would like to keep the original engine as it is numbers matching. Thoughts about resleeving vs a different block?

[tzei]

So what is the bore now?

[Shonick]

I don't have those numbers yet. Just trying to be proactive in term of my decision making.

[kbmb02]

I recognize you didn’t ask this…

 

Ask your machinist to measure - and/or rough bore the existing block - to determine what size bore you’d end up with. Then, take that number and hunt for pistons for that size. Or, have pistons made.

 

Else: Yes, the M10 blocks can be re-sleeved - about $100 a cylinder if I recall correctly (and, somewhat preferable to do all of them). -KB

[tzei]

Ok. So old cast block can take up to 92 mm if needs be (n/a). 90.5 mm is safe in boosted use. I have had no good experienced going bigger & hi boost applications but thats just me.

 

look for pistons/rings at this time too (prizes & quality varies) and don’t bore more than have to. Your maschinist should be able to say something about this i think.

 

from there you can decide to resleeve or new/ other block route.

[Conserv]

You’ve had great advice above. If your bores can be cleaned up at 90 mm or less, do that if you can find or have made pistons to match. I’m guessing your engine has a 121 head. But you need to focus on which head your engine has, a 121, or a later E12, or an even later E21. The pistons must fit the head. And sleeving, by a good machinist, works.

 

I’d also probably ask for the specs on all four cylinders before deciding on my approach to sleeving. Are all four cylinders equally worn, possibly re-bored once or twice previously? Or, for instance, is there one badly-pitted cylinder while the other three would clean up at first oversize (89.25 mm)? The latter is what I faced with my ‘76, where the head’s cooling jacket had corroded through on cylinder 1, admitting coolant and creating rust in cylinder 1, while the other 3 cylinders could be cleaned up handily with a first oversize re-bore.

 

While I chose to only sleeve cylinder 1, I considered sleeving all four and moving to standard size pistons. If, for instance, I had been able to find a set of 9.3:1 Mahles, for an E21 head (E21, not E12), in standard size, I perhaps would have sleeved all four cylinders. But since 9.3 Mahle pistons for E21 heads (they only were used on some Euro-spec e21 cars) were nowhere to be found, in any size, and I was having custom pistons made (9.5!), I chose to sleeve cylinder 1 alone.

Here’s my sleeved ‘76.

 

Regards,

 

Steve

 

[Shonick]

I agree Steve, excellent advice and I truly appreciate all the input.

[Mike Self]

From the originality side...unmodified early '02s (68s and 69s) are few and far between--there weren't that many sold in the first place when compared with later years, and time/rust/overenthusiastic modifiers have taken their toll. 

 

Having a matching engine is always a Good Thing, and especially on an early car--so if the block can be salvaged, I'd definitely sleeve it--per Steve's suggestion--one bad one if that's all there is, or all four if the bores are all hopelessly damaged.  A good dry sleeve job is as good as an original block and is done all the time for heavy machinery.

 

mike

[andyleonard]

We have a kid-driven 68 2002 here that was sleeved in one hole by L.A. Sleeve for $50 in 1972. Every time it gets rebuilt - I think we're on #4 - I show the block to an established engine builder who proclaims it "junk" and every time I say a bad word, have it sleeved in a different hole and off we go. Currently we're at 10.2-1 with a cam, dell'Ortos  fancy head and 12 # flywheel ...and some of the kids have kids but it's the same block. 

 

If a sleeve works for a million miles in a semi, it'll probably work in your 2002.

[Son of Marty]

Just for them record almost all over the road diesel engines use wet sleeves, so in other words the cylinder lifts out and is replaced with a whole new one, most auto engines the cylinder is cast with the block and won't come out and it can be rebored larger or added to or resleved.

[Mike Self]

1 hour ago, Son of Marty said:

almost all over the road diesel engines use wet sleeves, so in other words the cylinder lifts out and is replaced with a whole new one, most auto engines the cylinder is cast with the block

Notable exceptions are most of the Triumph TR-2/3/4/5 sports cars (engine derived from a tractor engine, IIRC), Peugeots at least as long as they were imported into the US (and perhaps still), TA and DS series Citroens and Renaults well into the early 90s. 

 

One of the pluses for wet liner engines was that the blocks could be cast of slightly softer cast iron, for easier machining, while the cylinder barrels could be centrifugally cast from much harder iron for better metal grain and longer life.

 

And its easier to change displacement simply by fitting cylinders with larger bores.  The Renault 662/670 block was fitted with pistons ranging from 54.5mm in diameter to 62mm depending on the cylinder barrels.  Try that with an all-in-one block!

 

mike  

[bergie33]

For whatever it's worth, when I just had my engine block done ('74 tii), I had the option to bore to 90mm, sleeve the block or find a replacement block.  Since my engine was already a factory replacement, so no matching numbers, I opted to use another good block that I had.  In your case, with matching numbers, I would sleeve it if you are already bored near the max.

[02Les]

20 hours ago, andyleonard said:

Every time it gets rebuilt - I think we're on #4

Hmmm, that's a lot of rebuilds. Why did you/someone have to keep rebuilding it.

[chargin]

It's not a Muscle Car, personally none of my 02 friends ever looked at the engine number to see if it matched.

It may matter to you but most wont care, either way best wishes 

[Greg Mierz]

Sleeves work well if done right, I've got over 30years on the one in my block and its is still running great.