Rebuilding an m20b25, after measures were taken need new 84.25mm pistons.
Stock BMW Mahle might not be available anymore.
Lot of aftermarket forged options (IE/Ross, Wossner, CP, Wiseco, ..)
My goal is to buy the most durable/well built ones. Longevity is my priority, not performance.
Ideally would prefer to purchase in EU but open to buy in the US.
Any advice would be very appreciated, thanks!
m20b25 rebuild need advice for purchasing new pistons
Moderator: martauto
Get a block from a late M20B20 and bore it out to 84mm then use your old std size pistons.
You have to bore and hone your old block out to 0.25 oversize anyway, it may be your best option unless you need to keep the engine number.
Shouldn't be hard to find a knackered 320i engine, it can have worn bores too, doesn't matter. Lots have been stripped for their con rods for stroker engines
You have to bore and hone your old block out to 0.25 oversize anyway, it may be your best option unless you need to keep the engine number.
Shouldn't be hard to find a knackered 320i engine, it can have worn bores too, doesn't matter. Lots have been stripped for their con rods for stroker engines
get the Mahle MS 2.9L ones 85mm bore 10:1 CR from IE. They are a good street piston with OE offset dish and raised dome that actually generates proper mixture motion. also they are a high silicon content alloy so lower expansion and better wear. They suit a M52B28 crank and 135mm rods stock or ones from a 24V.
you could theoretically run these with a stock b25 crank with M50 140mm rods rods but might need a custom thickness HG but might not depend if its a virgin block or been decked/skimmed.
do not under any circumstances get Ross, CP, Wossner etc as they will almost certainly be the wrong alloy for what you want and the wrong dome shape screwing up the burn characteristics. These places typically use a low silicon alloy which is far from ideal. they may have the correct alloy but depends on the forging blanks they have and then you'd need to send a OE cast piston to be scanned and copied.
you could theoretically run these with a stock b25 crank with M50 140mm rods rods but might need a custom thickness HG but might not depend if its a virgin block or been decked/skimmed.
do not under any circumstances get Ross, CP, Wossner etc as they will almost certainly be the wrong alloy for what you want and the wrong dome shape screwing up the burn characteristics. These places typically use a low silicon alloy which is far from ideal. they may have the correct alloy but depends on the forging blanks they have and then you'd need to send a OE cast piston to be scanned and copied.
E30 325is with M20B31