i just bought a 347 kit and got the block back from the machinist. looking at the specs from kb piston bore clearance should be .0015-.002. when i went to install a ringless piston to check clearances i can fit a .005 feeler gauge between the piston skirt and bore. i gave them the pistons and the spec sheet to them and told them what it should be at. is this acceptable or should i get grumpy with the machinist?
Well, I think that you would check this by trying to insert a .002 - .003" feeler on each side of the piston (180 degrees opposed) as you are, I think, doubling the clearance by having the side opposite your .005" feeler against the cylinder wall. Is that right? I believe that there is a specific spot on the piston where clearance is checked. I don't remember if it is done at the skirt, or somewhere else. I didn't check my machine shop's work, so you are doing more than I did. Good going. Okay, checked up on this, and it IS checked at the skirt, at the level of the balance pad.
i would talk to the machinist and find out why he set the clearances at .005 rather than .0015. and then let him know that he owes you for a set of pistons, or he can sleeve the block and set the clearances right for you. either way he needs to fix this.
Piston Way to loose, he is responsible. What you have now is junk if you are checking 90 degrees to wrist pin. Some other brand pistons do fit that loose.
some further checking i see that all the pistons are dead on the same, using the same hole. when checking them i put them i upside down and measure at the center of the skirt. .005 passes easily the whole length of the feeler gauge on all holes, and .006 will fit tight in a few of them. maybee tomorrow ill be calm enough to talk with the machinist with a straight head.
well i ended up pulling the engine out of my old mans beater and replaced it with my 302 the stroker will be replacing. i took this block to a different machinist and told him what happened. he told me not to worry he'll take his time and get it dead on. it took about 2 weeks for him to get it done, but hell he got it right. i didnt even need to measure to tell, i just put a piston in and felt so much tighter just a little bit of rock to it no slop. .0015 feeler gauge snug in most .002 tight.
If you've got KB hypereutectics, he screwed up. If they're KB forgings, they're within spec. Go look this up on KB's site.
