3.1 stroker? on boost?? ..anyone?

[4evere30]

nothing else from another car would work?

[MF DOOM]

IIRC, boring .040 over will not raise your displacment by 1l. Youll get around .6l more? I have 85mm pistons in my m42 and it raised displacment to 1838cc. 1mm does not equal 1l.

[digger]

each 1mm gives approx 70cc on a 89.6mm stroke

[MF DOOM]

^^^Thank you for clearing things up.

[nando]

If you want a solid bottom end that uses bolt on parts, I'd go for am M52B28 crank/rod/pistons. The piston crowns are thick so you can shave them down and cut new valve pockets for the 2v head.

if you want the S50 or S52 crank, you're pretty much stuck with custom pistons.

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

you're on crack. Why even bother posting this kind of crap? If you don't like M20s, then just don't post in a thread about M20s.

[nando]

You don't HAVE to bore the block anymore, you will still be at 3.0L (2979cc) with 84mm bore, but you will still need custom pistons because of the change in stroke. Since you have to use custom pistons anyways it would be pointless to not go to a bigger bore, IMO. 85mm will yield you a 3.1L M20 and 86mm will yield you 3.2L, although I hear the cylinder walls are dangerously thin for boost at 86mm.

people say this all the time, but there's no proof that 86mm is too thin for boost.

S54B32 has the same cylinder spacing as an M20, an even larger bore, and they work with boost just fine..

[Killacortes]

I probably want to say tired of M20. With 24v engines being cheap now, I would not even think about M20 3.1L. Even non vanos M50 is better than M20 3.1L.

Never go full retard

[dustyperez]

I am in the process of doing this build as well. I have looked and calculated for hours and hours. no pistons are quite right for the bigger stroke. you either need to shave skirts or tops of pistons, deck the block a large amount or use a super thick gasket.
here are some piston dimensions and whatever
http://cars.forumsee.com/a/m/s/p12-1...ion-ratio.html

IMO if your goin thru all this trouble why use a stock piston. Ive decided to got with cp's from vac. they are a little over 1k and they have all the specs already.