Floating piston pins - Fitting of conrods

Competition engines and ancillaries - general discussion
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Floating piston pins - Fitting of conrods

Post by Christopher_205Rallye » November 13th, 2006, 12:07 pm

I have some peugeot sport Mahle forged pistons that have fully floating pins. (They are designed for a 1294cc 205 Rallye)

I am not using these right now. However I have been offered a set of modfied connecting rods that have been modfied to fit forged pistons. The measurement of the small ends are claimed to be 20mm.

I measured the pins on my pistons (with a digital slide) and I measure 19.98, 19.97.

I have little knowledge of the tolerance in the fitting of floating pistons. Does this sound like a good fit for my pistons. Or am I better off getting someone to machine my standard conrods to fit (which are normally a smaller interference fit)?



Guy Croft
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Post by Guy Croft » November 13th, 2006, 12:35 pm

Hello Chris

those pins would be way too loose, rattle and knock the rods to pieces, you need about 0.008mm clearance for a good sliding fit rod-pin. rod bush-pin fits are a job for the expert only (ie: rod manufacturer).

Better to get some race rods made. I use only Calif based Cunningham as it happens but UK Arrows do race rods too and are a nice firm to deal with.

FWIW you are on the right lines, I'd never run press fit pins for choice.


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