I got an email from Jim, the owner of the machine shop. I can actually tell you how much my sandblasting (40psi) and 400 grit paper piston cleaning method made when it comes to piston to cylinder clearance! This is what he said:
Specs call for .0015"-.0025" piston to block clearance. The block only varies .001 taper from the bottom to within 1 inch of the top. However the bottom of the cylinder is .002" over .060" giving us .004"-.0045" clearance. I don't believe the clearance has changed more than .0005" with cleaning the pistons and honing the cylinders. This can be reduced by knurling the pistons. The top ring groove on the pistons is also worn enough that they should be machined for a ring groove spacer to bring that back to standard clearance. Cost for knurling and ring spacers is $89.70 for the set. .080" pistons are $124.26 a set. This engine was running with that clearance when it was assembled the last time. It has a long skirt piston that lessens the need for a tight clearance and I know people run them this loose but I don't know if they have any noise or blowby. The ring end gap will increase by .006". Let me know if you want run like it is or bore it .080".
I am instructing him to go ahead and go .080 over. I do not want to pay for all of this machine work only to have too loose of an engine and blowby. Does this make sense?
