Do I need to bore over 30 to put in pistons?

[Billla]

Originally Posted by Blue71LWB

I'm thinking of putting in some flat top pistons in my inline 250. I feel the engine is fine , but I was told I would need to have it bored if I was going to go with new pistons. I really don't want to bore the block. So will it be OK , to put in new ones without boring ?

Pistons come in different oversizes - .010, .020, .030 and so on. Somtimes there is an .002 or .003 piston as what's called a "high limit" piston - allowing a new piston to be installed after a quick flexi-hone if there's minimal bore wear.

It all starts with a bore measurement - the bore determines what your options are. Once the largest bore size is known, then you know what your options are. Sometimes the inline 6's show little or no bore wear even after 100's of thousands of miles.