Question about Strokers

[User Name 19]

OK Guys, Maybe not right place to ask, but i can always move it if needed

i am thinking about stroking my M30 - now i know the available options some of which arnt going to happen cause or rareity of parts

but i just wanted to know, how you change a crank shaft to increase stroke on a engine i read some stuff on the net but i am actually lost and throught someone might bout to put it in english haha

eg. say i want to increase the stroke on the m30 to 94mm which would increase the capacity to around 4 litres.

could you do this using 3.5l crank modified etc -

im prob sure that i would need a custom crank for something like this $$$$ but what are the possiblitys or just a explaination - how grinding etc a crank shaft would increase stroke

Cheers

kym

[BM WORLD 1286]

you wont get 4L easily . using readily availible parts teh best is about 3.6L

easist option is a 3.5l from a e34 , e32 etc.

or e28 , e23, e24

or go for the early very 3.5L with 84mm and fit the later 3.5l 86mm crank etc and get about close to about 3.6L

if you do a over bore with custom pistons then you get some where near 3.7L

[User Name 19]

Thanks Brent

see the options available and i now you can make close to 3.7l like marty did which is good,

but still comes down to would really like to know how you change a crankshaft by griding etc makes no sense

and would be soo keen for a 4 ltr M30 turbo think it would be something new its the cost of the custom crank

quoted around 3.5k US im sure itl be arround the same in nz - is the power gain worth the $$$ or do i just put that cash into making the build slighltly more engineered

[conrod 1]

but still comes down to would really like to know how you change a crankshaft by griding etc makes no sense

It is called "offset grinding" and what the engine ship does is grind the bearings for the big ends off centre to where they were, the centres are ground further away from the crankshaft centreline, which is a cheap way of making a "stroker" crank. What it also means is that the big ends are now smaller in diameter than they used to be (not always a bad thing) so you need to find rods and bearings to match the smaller size. Only really achievable on some engines, and the gains are usually only 200cc or so. So probably not a cost effective solution for you, it usually a last resort to squeeze more capacity out of an engine when no other options exist.