Guys , I have been doing a bit of reading on Piston Skirt clearance for race engines and I looking for some advice on other people experiences, currently I am running 5 thou ??, Vizard reckons some people run up to 10 thou ??



Mal

10 thou seems way too high to me. When I ran forged Mahle flat tops in the 1310 I used 3-1/2 thou.
Why not ring GR and ask him? He doesn't bite... (usually)

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

might just do that M

Pistons are like chocolate cakes all the same name but all different. Most are not round as to cater for thermal expansion, clearance will vary on piston. Forged, cast, thixotropic formed. If you stress plate hone the bores then you can reduce clearance. If you shorten the skirt less clearance. The aim is minimum clearance without galling. Most forged pistons worked on used 5 thou but an austcar that was quite successful ran 10. If you run 10 and piston slap is to noisy then fill the piston with shot and press them to swell the piston 5 thou.

Piston swelling is a lost process to the professional market. Maybe a howto in the future.

Pressing sounds pretty intense!

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SooperDooperMiniCooperExpertEngineering

All garage work involves equal measures of enthusiasm, ingenuity and a fair degree of irresponsibility.

You can also have the piston skirts coated with some sort of 'high-performance' coating which is about 0.003" thick.

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Curly
'64 Cooper 'S' (Group Nb spec)
'67 Mini Marcos GT www.mm7056.wordpress.com