5 replies to this topic

[Leekr89]

slowly building up a fast road engine for my mini and im just wondering if any of you guys know what bore size i need to go to fit 1275 +60 pistons? as ive just been speaking to my local machine shop and they asked me what exact size i need the cylinders boring out to, thanks in advance :)

[dklawson]

DO NOT give the shop a figure/value. In fact... I am surprised they are asking you. It makes me question if they know what they are doing.

Tell them to wait until you can supply the new pistons. The pistons will come with a data card that tell what clearance to bore to over the diameter of the pistons. The shop is supposed to measure the pistons you are going to use and bore the block to fit the exact pistons you have. There is not a "one size fits all" number to bore to.

[Klevdo2202]

Adding to what dklawson has said, the machine shop should be advising you what size to go for, by looking at the size/condition of bores. This is what I did when I had my MG Metro engine rebored.

[lrostoke]

plus one for Doug's info...its exactly what our machine shop did, they had the block and pistons and machined to suit the pistons.

I guess as far as advising what size go for it may be the OP as an engine size in mind he wants rather than boring out because of wear and tear

[Turbo Phil]

If they're going to bore your block without even seeing the pistons, go to another machine shop.

[Leekr89]

thats originally what i thought when he asked me, i already have the pistons and he didnt ask me for them, and it sounded like he didnt know what he was doing hence me writing up on the forum, he said he will do me a good price because i mot his cars, think i'll leave it and find somewhere else. thanks for your help guys :)