I have a LS7 with about 7k miles on it w/-14cc dish pistons,4.125 bore.I want to go to flat top pistons.Can I just swap them out w/ LSx 4.125 flat top pistons without honing out the cylinder's or anything else....................Paul

 

I would like to know the answer to this as well.

 

I would hone and balance.

 

I don't want to take the motor out of the car though.I want to drop the cradle and the oil pan & take the heads off.What about if I weigh each piston & rod as they come out and put the new piston on the rod and weigh that................Paul

 

After you do all that,you'll wish you wold have just pulled the motor.That's just my opinion.

 

You can't weigh the piston and rod as one. All of the piston and part of the rod is reciprocating weight, part of the rod is rotating weight. Chances are there will be enough difference in weights that the crank will need to be rebalanced. I'd pull it and run a dingle berry hone thru the bores, clean it and reassemble after checking out the balance issues.

 

re-balance at the minimum

 

Well there goes that idea.Thanks guy's...................Paul

 

The cylinders would need to be honed only if you have to use different rings. Going from a dish, to flat tops will probably suffer significant weight difference. Doing all that work with the engine in the car probably isn't a good idea. I agree, you'll probably wish you just pulled the engine out in the end.