m20b20 over bore

[makman]

Ive got a b20 in brilliant condition...runs realy well and has just had a cam belt kit and new cylinder head, rockers, valves etc done by the previous owner. ive got a 2.5 inlet manifold, throttle body and injectors coming for it which i picked up for cheap but im wanting to extract some more umf..

My plans were to bore it out and fit larger pistons and crank to raise the diaplacement, now ino the 525e bottom end is perfect for this but its hard to find one and id rather have a nice set of re honed bores and my block (inl the history and ino how well its been taken care of)

So what im asking is which crank and pistons can i use and whats the best methods and so on! Thankyou

[HairyScreech]

if your going for a cheep stroker then the best bet with what you already have may be to get a complete m52 b28 internal set (crank rods and flat top pistons) and have your block bored to 84mm.
all that will be needed from there is an engineering shop to skim and pocket the flat 24v pistons and that should work.
unfortunately this is a method that is very much still in development, the sweedish guy doing it has gone quiet for a while and i have had no time to really work out the details.

the tried and tested method is to either put an eta bottom end on your head etc, although most eta blocks are now worn out scrap
the other option is to add 320 rods and a m52b28 crank to the m20b25

[makman]

Mmm okay mate thanks for that. is they no other option on the pistons then, such as m52 crank, 320 rods, bored 320 block, 731 head and some other stock pistons? Im new to bmws lol, give me a vw and il do enything aha.

[HairyScreech]

eta piston may work, but its simpler to fit the whole eta engine and fit the 731 head to that.

as there is two easy routes (2.7 eta if your 731 headed and 2.8 +320 rods if your 885 headed) then there hasnt really been much experimentation as far as odd combinations go.

[makman]

Think im just gonna try find an eta block and rebuild it all then pop my head on and match the ports to my new 2.5 manifold and tb...got the 2.5 injectors too. What po wer would that net with a decent 6 branch and a chip dya think? Thanks

[TheMeathead]

Just woundering if anyone had tryed a b20 bottom end, 84mm dished b25 pistons and a 885 head?

Im curious as to how well this would work? Im guessing it would be quite a perky engine.
Also the displacement (2.2l??) any ideas what that would be?

[ross2009]

Just woundering if anyone had tryed a b20 bottom end, 84mm dished b25 pistons and a 885 head?

Im curious as to how well this would work? Im guessing it would be quite a perky engine.
Also the displacement (2.2l??) any ideas what that would be?

You won't fit 84mm pistons in a b20 the 2ltr are 80mm bore if you bore it to 84mm it's basically a 2.5
So you might as well buy a 2.5 straight out lol

[fowler]

Or bore the block use an eta or TD (have one here with me ) and build a 2.7 stroker 2.8 is a good build but from i know you can make a screamer 2.7 making 240 bhp if tuned correctly

[ross2009]

ha you really are a proper sales man aint ya ben lol

[fowler]

lol