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kiwi pip
02-19-2007, 03:50 AM
Is it possible to machine the top of b25 pistons flat,so that i can fit a731 (320i)head onto the b25 block,has anyone done this or could put me in the right direction,Phil.

peerless
02-19-2007, 12:33 PM
Is it possible to machine the top of b25 pistons flat,so that i can fit a731 (320i)head onto the b25 block,has anyone done this or could put me in the right direction,Phil.

Anything is possible, but is it cost effective?

Has your 731 head been upgraded to the bigger valves? Remember they come with the smaller eta sized valves becuase they where only running a 80mm bore, regardless of the their rated rpm.

Also in your other post you mentioned going to 86mm bore which would mean youll need custom pistons.

You can machine the stock pistons but you have to make sure to leave enough crown height and piston top thickness. I wouldnt recommend it.

Call metric mechanic, they are very helpful. Just be aware their custom pistons will run you about $1,100.

Or, you could go with a 2.7 bottom end, 731 head, 2.5 intake and electronics. Use a little of all 3 motors. :)

Have Fun.