I'm having my 6.0L gen4 block bored to clean up a slightly worn cylinder #6. I'm thinking .020" will clean it up but might have it bored .030". I'm lost as to how piston domes and inverted domes are measured. Is a factory piston the baseline for + or - cc? I'm trying to find a piston set that will keep the compression same as stock with a 4.020"-4.030" bore. I find summit racing's website confusing. Any help would be greatly appreciated.

 

I used speed pro 4.030 pistons part#H1128CT75MM in my budget build. Hyperutectic piston with coated skirts. Not forged anything special but a good replacement for $250 .
Great for a mild build

 

I don't think that you should worry about the minimal compression increase that would come from a .030" over bore.

 

The stock pistons have a slight dish in them with valve reliefs. Finding a piston exactly the same .030 bigger is a sure challenge. I checked GM parts and GM offers a piston .5mm over sized but that's less than .020" and their $65 a piece.

 

The ones I listed are stock replacement and stock compression. They have a slight dish just like the factory piston .

 

My stock pistons have a dish like the one you have pictured but with two valve reliefs. Is the valve relief for vvt engines. I'm doing away with the vvt