My block need to get a slight bore/hone. I will not know untill I take it to the machine shop how much. I wanted to go with CP pistons but the shelf ones are either 84 or 84.5. I was looking for somehing in the middle. I know I can special order them but it is 3 weeks and a extra 100. If I have to I will but just wondering whats out there in different size or brand but of the same quality.
Gsr bolck, looking for around 9:1, turbo motor with somewere around 800 whp.

 

they won't make them cause nobody makes rings for it

 

I think it need to go .020 over. Anyone mad a ring set for that pize piston

 

.020 inches = .5 mm. Nothing wrong with 84.5.

 

I am hoping it will only need .010, But .020 will definatly be enouf. Ist it worth getting custom pistons for .010 over or should I just go with the 84.5? The block is Oringed with 1/2" head studs.

 

 

Rather than spending an extra few hundred dollars and wasting weeks worth of time, just overbore that extra .010" and go with a set of shelf pistons. I really dont see how this is a hard decision

 

well, your right going to a 84.5 piston would be easy way to go. But I am going for some very high number with this motor and when your running that kind of hp something so small as .010 might make a big difference in keeping the headgasket from leaking.

 

Like was already stated a 84.25mm ring set may not be available.Custom ring sets can usually be made,but I would leave that as a last resort.I have had a couple sets made and I was not impressed with the results.My vote would be for the 84.5mm.

 

84.5 will seal up just fine under high boost.