Anyone have experiance with the M88 engine?

[Jeff N.]

Trying to find out what the tolerable compression numbers are for a healthy engine.

BMW says 10 to 11 bar. They tend to be low of course as they don't want to fix stuff. Other suggest numbers should be in the 200+lb range.

Lowell - you guys see these things? (early S38 euro engine... the 10.5:1 variety)

[genphreak]

Trying to find out what the tolerable compression numbers are for a healthy engine.

BMW says 10 to 11 bar. They tend to be low of course as they don't want to fix stuff. Other suggest numbers should be in the 200+lb range.

Lowell - you guys see these things? (early S38 euro engine... the 10.5:1 variety)If 10.5:1 it is an S38B35.

M535, M635 from 1981 all had these with Motronic. Later cars (M5 & M6) had the catalysed S38B36 and S38B38), except the euro ones which stayed S38B35 (with updated Motronic?) - I'm not 100% of this. If 10.5:1 that would make it one of the non-catalyst versions- the best of all... due to the higher compression and more aggressive cam.

If not S38 it could only be a BMW designated M88/1 (M1 cars only) unless it is an an experimental engine for the e26 M1 (circa 1977) M49/5, or perhaps an even earlier M49/? twin cam from a 3.0CS/CSL... all these used Kugelfischer injection and dry-sumps though. Any idea about the engine's history?

[Jeff N.]

Nice engine history, you're pretty much spot on. The M88 is the designation for a non-cat S38.

Got any idea what "good to better" compression is? It was pushing about 180 to 190 across.


If 10.5:1 it is an S38B35.

M535, M635 from 1981 all had these with Motronic. Later cars (M5 & M6) had the catalysed S38B36 and S38B38), except the euro ones which stayed S38B35 (with updated Motronic?) - I'm not 100% of this. If 10.5:1 that would make it one of the non-catalyst versions- the best of all... due to the higher compression and more aggressive cam.

If not S38 it could only be a BMW designated M88/1 (M1 cars only) unless it is an an experimental engine for the e26 M1 (circa 1977) M49/5, or perhaps an even earlier M49/? twin cam from a 3.0CS/CSL... all these used Kugelfischer injection and dry-sumps though. Any idea about the engine's history?

[genphreak]

Nice engine history, you're pretty much spot on. The M88 is the designation for a non-cat S38.

Got any idea what "good to better" compression is? It was pushing about 180 to 190 across.Sorry Jeff, I'm no practical expert with M88s, I've never worked on one. If I was in the US I would be tho, they are just so rare here in Oz. One day I will buy one tho and do a blueprint and slow, careful rebuild. These engines deserve preservation as they were the best in their era. No doubt Whit will know the pressure numbers you need- which reminds me, I have to test my M30B35s bores too... they just looked good to me when I had the head off the block, all the original honing was there and I couldn't even detect a lip worn anywhere towards the top of the bores... which was good enough for us to finish the job with no more adieu at the time.:) nick