pureboiracer 0 Report post Posted June 9, 2009 Hey guys. thinking of building up a head for an m20b25. does anyone know if the 731 head will fit on? also are there many gains to be made from honing and flowbenching? What are the common mods done to m20 heads for performance? And last but not least what is the ideal cam to run in a racecar that wont rev above 7 and uses stock pistons and bottom end? dont really care how "streetable" it is. just want it to go fast. lol Any info will be apreciated. cheers guys. Quote Share this post Link to post Share on other sites
|ncary 0 Report post Posted June 9, 2009 According to a pro flow tester on E30 Zone (UK E30 forum) the 325i head flows better than the 323i head. I'll link the thread, a lot to read, amazing work by this guy, but you have to sign up to see it. http://www.e30zone.net/modules.php?name=Fo...pic&t=87664 A common M20 mod is adding 30 to it. (M50 ) Quote Share this post Link to post Share on other sites
Guest FrantiC Report post Posted June 9, 2009 All the heads can fit on either or models really.. But 731 head on 2.5 bottem end isn't gonna be better at all. m20b25 has domed pistons and designed together with the 885 heads combustion chambers. 731 head suits a b27 ETA bottem end, So it's good in a stroker build and does not drop compression ratio like the 885 head does. So you could in effect have a 10.2 or 11:1 CR 2.7 stroker by putting the 731 head on the ETA 2.7 bottem end.. 731 head on the b25 would probably raise compression I would guess? Other than checking valve clearances with the b25 pistons, it will bolt down fine. Quote Share this post Link to post Share on other sites
