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Home > Help Needed / General Tech Chat > Ideal piston clearance ???

Rod S

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5988 Posts
Member #: 2024
Formally Retired

Rural Suffolk

22nd Jan, 2008 at 01:04:04pm

As above really, for 1360 (Using the 73.0mm pistons from MiniSport Australia) and say max 8-10psi boost (just for road use) and CR 8.3 or less (depending on how much I can safely machine out of the pistons, yet to be determined, and how much I can take out of the head).

I've read the threads (and seen the pictures) of where people have had problems with scuffing and pick-up and then been given advice on maximum acceptable skirt clearances after re-honing, but what's a good starting point (bottom of skirt) for a new bore?

The two Haynes (Mini vs Metro) don't say the same but even their average (0015 - 0025) seems a bit tight for the extra heat from a turbo.

I would rather instruct the machine shop than let them guess!

Rod.

Schrödinger's cat - so which one am I ???

Vegard

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7765 Posts
Member #: 74
I pick holes in everything..

Chief ancient post excavator

Norway

22nd Jan, 2008 at 01:52:51pm

I use 0.006mm on must stuff. That's the upper side of what you're quoted. Seems to work..

On 13th Jul, 2012 Ben H said:
Mine gets in the way a bit, but only when it is up. If it is down it does not cause a problem.

wil_h

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9258 Posts
Member #: 123
Post Whore

Betwix Harrogate and York

22nd Jan, 2008 at 03:22:06pm

Go for the maxim stated i.e. 2.5thou".

I have 4 thou on mine as I had problems, it's a low mileage race engine though and burning a bit of extra oil isn't a problem.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph



On 2nd Jan, 2013 fastcarl said:
the design shows a distinct lack of imagination,
talk about starting off with a clean sheet of paper, then not bothering to fucking draw on it,lol

On 20th Apr, 2012 Paul S said:
I'm mainly concerned about swirl in the runners caused by the tangential entry.

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