getting my 1998 outback  dohc ej25 bored to 100mm , but  i`ve  mistakingly ordered sohc  pistons with the 4 valve reliefs  , my old  dohc pistons have the square dish.

 

i know i have to get 100mm head gaskets , but  will i have to get     thicker hg`s ?

 

 

 

Thinner head gaskets. 

 

Why are you boring it oversized? That's just a gigantic waste of time on an NA block. Get a new set of case halves or find a used set and have the main line honed. Cylinder walls are not a problem on Subaru engines, the main bearing clearances are the problem you need to address. 

 

GD

uhg.

 

100mm?  why?  Your cylinder sleeves are gonna be paper thin now.  On a phase I block? Now those tall barrels around the liner will be even more prone to vibration and losing Headgaskets.   

 

That engine won't last long.