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Message: <blockquote data-quote="leforte" data-source="post: 198171" data-attributes="member: 1943">please bear in mind the cylinder head for the m50b20 and m50b25 have different valve sizes be it inlet valves or exhaust. m50b20 has a 30mm inlet/ 27mm exhaust, while the m50b25 has 33mm inlet/ 30mm exhaust.you can rebore your b20 block to accept the b25 pistons but all the valve cutout on the b25 pistons are different  and that itself can destroy or bend all the valves in the b20 head. however if you have a vanos m50b20 in your car now, you can try at your own risk using the crank and conrods from the b25 mated to your original piston and head with b25 vanos cams from pussy, that will give you a smaller capacity than a original b25 but the longer stroke will give you a vast torque improvement. you may need the dme from the b25 as well.</blockquote>