m30b34 block (e28 535) and m30b35 head (e34 535)-possible?

[daicos35]

Hi team, I have four questions.
1-Do the cooling channels on the late head (b35), line up with earlier block (b34), enabling the use of either gasket? (bore is the same).
2- Does anyone know the exact difference in combustion chamber size between the m30b34 head and the m30b35 head, and therefore how much compression drops when you do it?
3-What are the advantages/disadvantges of forged versus cast pistons?
4-Did they use forged or cast pistons in the DOHC e24 M6 (m635) engine euro or usa version?
thx for your help, Mike

 

[x_atlas0]

1. Yes, you can use the B35 head on the B34 block. Gives the same CR (or very very close) as the B34 head. I think it is like 7.9:1 or so. Todd at TCD has made a few motors like that.
2. Answered in 1.
3. Forged pistons are stronger and lighter than cast. This extends beyond pistons, as the forging process will always yeild stronger materials for similar weight. The main use of forged pistons in car motors is to allow them to handle boost or to reduce weight without compromising strength. The M30 pistons, if I recall right have always been cast, with the cranks being forged.
4. The S38 used cast pistons in all versions, (even the S38B38) if I recall right.

 

[velocewest]

1. They are compatible. Head gasket should be picked to match the block.

2. M30B34 (actually all earlier heads) is 58 cc's, M30B35 is 65 cc's. All other things being equal, this will reduce your compression ration by .75, or for example, 9:1 to 8.25:1.

3. Forged advantage -- equally strong with less weight. Slightly less expansion/contraction with heating and cooling, allowing closer fitment tolerance. Disadvantage -- can be more expensive, unless you buy VW pistons instead of BMW, then they'll be significantly cheaper.

4. Dunno.