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Simon (251ENG) may be able to give you some advice, there are plenty of custom piston manufacturers who would be able to make you a set, it's mainly a case of what your budget is.

For ease of build it may be worth considering a change to 998cc

Thanks mark, simon just contacted me so I hope he can help me out.. i'm starting to realize the trouble i'm getting into with the 850, but as long as I can get pistons I think it'll be alright. I'm torn between the fact that this is the original engine and makes a rather unusual project, and the fact that the parts I got would make a more significant change on an 998 as well as being safer..

From distant memory, the late 850 Minis (78-79) had solid skirt pistons. It could be worth contacting Unipart as well, as the Cowley warehouse had loads of this sort of stuff. Mini Mail also had some new 850 blocks and cranks, but we're going back a few years now.

I'd do an 850 just for the hell of it because it's the original Mini engine. I would have thought that with a decent head such as the 12G295, a 270 degree cam, 10:1 compression and a good exhaust, an 850 on a single 1.5 inch SU would make a reliable 45 - 50 bhp and be very driveable. They didn't have cam bearings but that shouldn't be an issue with a 270 cam.

mk1 wrote:Do a search on 850 tuning on this forum, there has been a lot said about tuning 850's in the past.

Search term used: 850 tuning ignored: 850

850 is always ignored by search engine