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Old 9th January 2017, 13:20
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Originally Posted by morris View Post
Hi All,

Does anyone out there have a spare 2.5 M50 block? My current M50B30 stroker project has hit a small snag when I took all my parts to the local machine shop today. Basically the bores on my M50B25 iron block are worn leaving a lip at the top that would instantly destroy the higher piston rings on the M54 pistons. My original idea was that just this lip could be cut out and the cylinder be honed but they've told me it needs a 0.25mm over bore and therefore new oversized pistons. The only ones we've found are 135 each + vat making that route totally uneconomical. Current options are

1. find a lower mileage M50B25 block that doesn't need a rebore, just a hone

2. Just rebuild the M54B30 as is and put the M50 back together

3. Find an M50B20 block and bore that from 80 - 84mm as everything else is the same - would be expensive on man hours though

4. Put the M50B25 back together again and accept defeat (don't see this as a real option)

I've seen some oversize M50B25 pistons for sale on ebay at a reasonable price so I could always still get the M50 block bored and rebuild as is. It will at least be resell-able then as an entire refurbished engine. Seller is Jazzman.0018 - is that you Patrick (recognised you have something very similar as your youtube name)
It seems to be a shame to give up on Option 1.
Somebody is bound to have an M50 block or engine lying around, it may just take a while to find it. I had a M52 328 block that I couldn't even give away and it end up in the scrap metal bin.
Have you tried on the BMW forums and maybe even the MOC forum who seem to be good at squirrelling things away?
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