42johnny

I took a piston out of the block and it mic'd out at 4.458,I thought 502's were 4.466 standard. was I told wrong?
If so what size do I have??
The guy who pulled my motors said they were new pistons and they look new.
Only markings on the pistons are SRP 75f ???
I need to get a ring set, even if these look good...

johnny

mike tkach

iTrader: (3)

the bore is 4.466.if your piston is 4.458 you have .008 piston to wall clearance.why did you remove the piston

42johnny

I was told it was a fresh rebuild on the motors when I bought the boat and the pistons looks great, but she had a spun #8 crank bearing. So I took care of the crank issue and trying to put it back together.
Other then that the motor looked good.
So I thought I should rering and light hone before it goes back together.

Johnny

Young Performance

You need to be sure about that piston clearance. The piston will be smaller than the 4.466 bore size. The cylinder clearance is built into the piston. You should measure the piston 1/2" above the bottom of the skirt. Service limit on those pistons is only about .005. Meaning, if you have more than .005 clearance, you need to bore and go to 4.500. Those pistons have a high silicone content and are designed to run fairly tight. They are set up from GM at about .003. If you get to much clearance between the piston and cylinder wall, they will break the skirts. I have seen guys run them at .006 and get away with it. Don't want to see you put it all together and have another problem. Just something to keep in mind.
Eddie

c_deezy

iTrader: (1)

Is piston to wall clearance measured as a total or half? Given the op's question, he has a difference of .008 between the bore and the piston. So given that, he should have .004 on each side of the piston, so wouldn't that make .004 his piston to wall clearance? So he should be within spec then correct?

Young Performance

No, it is total clearance. You have to take into account that the piston will rock from one side to the other. So, it can, and will, move .008 from one side to the other.
Eddie

c_deezy

iTrader: (1)

Ok that makes sense. Thanks for the clarification.