Hello.

I need some help arround the piston clerance, I have a Hepolite piston 83,00 mm but not now how much clerance must the barrel have.

BR, Mitja from Slovenia

email (option): mitja.peterka77@gmail.com

Hi, that must be a + 0.40" piston (= 1 mm oversize).
Look at the technical info at "engine clearences", see piston skirt clearence.

If it's an M20 and a solid skirt piston it should be .004" -.006" measured on the piston skirt thrust faces...Stated piston clearances vary slightly from publication to publication...The above are BSA figures.

If the piston is a 'split skirt' type clearances are MUCH smaller...

For a given skirt type bore/skirt clearances are the same for all standard overbore sizes..STD., +.020", +.040" and in aftermarket pistons +.060" ...Ian

email (option): ian@wright52.plus.com