decking block

i have a b17 i im going to use cp pistons 9:0:1 compresion my question is when you deck the block do gain compresion or lose compesion

Decking removes material. You gain compression

deck plates gain material, but so much you need custom rods. strictly for keeping a better rod/stroke ratio.

im just taking a little bit of material off just to get a good seal. Do you think i need to get customs rods still

No, like everything else mechanical, there is a service limit. If you stay below the limit, you don’t need anything custom.

Go beyond the service limit on the block and you’ll be shopping for a new one.

if you deck alot. Just clay the piston for clearence.

you have .030 before the piston tops are level with the deck. and you can actually go a bit over that.