Boring m30b35 from 92 to 93.4 mm, with 3.3L 88 mm crank.

[daicos35]

Has anyone bored the late m30b35 engine to 93.4 mm (FROM 92) ,and replaced the 86 mm crank with the 88 from a 3.3L?
Is this doable? Are there any major complications?
Does anyone know the webbing thickness between the cylinders once this is done?
Thx Mike

[Malc]

Yes it's do-able, expensive, but do-able
but it might be easier to source a 3.5 litre engine (M535 etc etc)
Don't know about wall thicknesses though
Malc

[velocewest]

Malc, the M30B35 is a 3.5 block. That's the M30 naming convention -- M30B28, M30B30, yada yada...

Daico, check out Paul Cain's car. You can find it by going into the "Links" section of this site. He's got a bored, stroked M30. If I recall correctly, the practical limit for bore on the 3.5 block is 94mm, but don't consider that gospel.

[Malc]

You know I haven't a "Scooby Doo" (clue) when it comes to all this engine code stuff! :oops:
All I know (subject to correction) is that the early BMW 6 cylinder engines basically had the same bore and capacity was twiddled with by changing the stroke

Yours embarrassed
Malc

[velocewest]

It more or less follows a pattern, and you can see it in the block markings (2,5/2,8 -- 3,0/3,3 -- 3,5).

2.5 to 2.8 = longer stroke (same block)
2.8 to 3.0 = bigger bore (new block)
3.0 to 3.3 = longer stroke (same block)
3.3 to 3.5 = bigger bore (new block)

Knowing this quite possibly makes me the biggest bore of all! :lol:

[ScottAndrews]

6 mm +/-

My M90 block has this bore and spacing and it uses the same head ans an M30.
S