Potential for a S50B30 crank to build a 2.85?
Posted: Sun Sep 18, 2011 3:23 pm
Just looking at a S50B30 crank on ebay and thinking, I wonder how easy it would be to build a 2.85 using the same principles as a 2.8 (I've just built a 2.8 and if I can do it etc etc)
Crank spec I've got of wikipedia is a stroke of 85.8 mm, as opposed to 84 for the 2.8. From what I can gather, this still fits in with the 1.5 stroke to con rod ratio (128.7mm against 130mm 320 rod).
Deck height could be taken care of by using the block that starts with a 206.5 deck height to start with (think I've read a post by Ant mentioning that block). My logic being I had to skim my block down to a deck height of 205.5, the stroke is 85.8mm which will make it stand 0.9 mm higher than the 84mm crank, so machine 0.1 from a 206.5 crank and you have the correct deck height.
Little bit more off the piston skirts and you have a 2.85 as opposed to a 2.79. Only a tiny advantage I guess but the M3 cranks look only a little bit more than a 2.8 crank.
Am I way off or is this doable?
Crank spec I've got of wikipedia is a stroke of 85.8 mm, as opposed to 84 for the 2.8. From what I can gather, this still fits in with the 1.5 stroke to con rod ratio (128.7mm against 130mm 320 rod).
Deck height could be taken care of by using the block that starts with a 206.5 deck height to start with (think I've read a post by Ant mentioning that block). My logic being I had to skim my block down to a deck height of 205.5, the stroke is 85.8mm which will make it stand 0.9 mm higher than the 84mm crank, so machine 0.1 from a 206.5 crank and you have the correct deck height.
Little bit more off the piston skirts and you have a 2.85 as opposed to a 2.79. Only a tiny advantage I guess but the M3 cranks look only a little bit more than a 2.8 crank.
Am I way off or is this doable?