Like the title says would i risk going into ptv problems if i switch to +cc pistons instead of my -4cc pistons?

 

Most aftermarket pistons have valve reliefs cut into them for just such a thing, so you should be ok. Still measure though if you have a big cam.

 

We would need more info on your setup. What head, valve size, cam specs (including intake centerline), etc. Eric L

 

Lq9 404 l92/ls3 current cam specs is a 230/244/621/598/114lsa ..valves are stock gm valves 2.165/1.59

 

Aftermarket pistons normally have valve reliefs. Net volume is just a taller dome to offset the valve pocket volume.

 

Not sure if your heads are milled or running thinner gaskets and the degree of advance with that cam, but it would clear on factory flatops no problem even if it had 6 degrees advance assuming the rest was stock.

 

My heads are milled .030 and the chambers are 64cc heads.. im trying to see whether to step it up to +dome pistons to get me 12:1 compression.

 

You could run a .040" head gasket and mill them to .048" and possibly be ok without swapping pistons, do they not have valve reliefs as others have mentioned?

 

The domed piston will still have valve reliefs cut on them, but you would really have to worry with as much as yo have milled the heads. You would DEF need a piston that has an L92 valve pocket on it. They increase the CR quite a bit. I have used them before and put them in a tbss with some trick flow heads in a 402. It moved pretty quick til the stock 4l70 broke.
The biggest issue is not knowing the PTD height/clearance. That will affect CR quite a bit as well as quench and piston to head clearance. With a domed piston, you normally do not have to worry about it effecting the quench as most of it is contoured to the chamber, but the pistons are set up en mass. They wont know every difference in every block or even if the deck height is the same side to side. That is up to the machine shop.

A few more things to think about. You can just get an aftermarket small chamber LS3 casting and work from there. If you mill any more you may run into other unforseen issues.

 

The domed piston will still have valve reliefs cut on them, but you would really have to worry with as much as yo have milled the heads. You would DEF need a piston that has an L92 valve pocket on it. They increase the CR quite a bit. I have used them before and put them in a tbss with some trick flow heads in a 402. It moved pretty quick til the stock 4l70 broke.
The biggest issue is not knowing the PTD height/clearance. That will affect CR quite a bit as well as quench and piston to head clearance. With a domed piston, you normally do not have to worry about it effecting the quench as most of it is contoured to the chamber, but the pistons are set up en mass. They wont know every difference in every block or even if the deck height is the same side to side. That is up to the machine shop.

A few more things to think about. You can just get an aftermarket small chamber LS3 casting and work from there. If you mill any more you may run into other unforseen issues.