Piston Size help

[sliderbkt]

I took my cylinder to my machinist today. He said they didn't need bored, just deglazed. The cylinders measure 2.54" or 64.5mm. Should I buy that size piston? Or, order 64.75mm and have the cylinders bored.

[tgbanshee]

I would say if your bores are clean with no nicks on the walls and the taper, out of round, and diameter are all within spec, then there is no point in getting them bored and wasting a bore size, BUT... The problem here is if you really want to do this right, you need to send the pistons to the machinist with the cylinders so the piston-wall clearance can be checked and the cylinders bored slightly to match the piston if necessary. So you run the risk of buying too small a piston if your bores are slightly too large and out of spec but can potentially save money if the bores are in spec and don't need to be enlarged and only need to be honed. If your measurement of 64.5mm is accurate, that is a .020" overbore piston. The motor will run if the bore is slightly too large and you go with 64.5mm pistons and only get it honed but compression will probably suffer and I for one just don't believe in doing things half ass, but what you choose to do is up to you. If you want to do it right, buy the pistons and send them to the machinist to have him match the bores to them.

Edited June 4, 2008 by tgbanshee

[sliderbkt]

I would say if your bores are clean with no nicks on the walls and the taper, out of round, and diameter are all within spec, then there is no point in getting them bored and wasting a bore size, BUT... The problem here is if you really want to do this right, you need to send the pistons to the machinist with the cylinders so the piston-wall clearance can be checked and the cylinders bored slightly to match the piston if necessary. So you run the risk of buying too small a piston if your bores are slightly too large and out of spec but can potentially save money if the bores are in spec and don't need to be enlarged and only need to be honed. If your measurement of 64.5mm is accurate, that is a .020" overbore piston. The motor will run if the bore is slightly too large and you go with 64.5mm pistons and only get it honed but compression will probably suffer and I for one just don't believe in doing things half ass, but what you choose to do is up to you. If you want to do it right, buy the pistons and send them to the machinist to have him match the bores to them.

 

Sounds good. i'll buy a set of .030 over pistons.

 

thanks man!