Piston to wall clearance question

[Fastjeff57]

I'm having an early Merc triple bored out .030 over and need to tell my boring dude what clearance I want.

Looked in my genuine Merc manual and couldn't find it. Anyone have a spec?

Thanks,

Jeff

[Powerabout]

I'm having an early Merc triple bored out .030 over and need to tell my boring dude what clearance I want.

Looked in my genuine Merc manual and couldn't find it. Anyone have a spec?

Thanks,

Jeff

if pistons are stock you add 030 to original bore size

[Aeroliner]

I'm having an early Merc triple bored out .030 over and need to tell my boring dude what clearance I want.

Looked in my genuine Merc manual and couldn't find it. Anyone have a spec?

Thanks,

Jeff

The new Wisco pistons I now stock for the 20, 40 and 60 cubic inch engine call for .0065 clearance. I also use that with my merc pistons we run in D mod

[Fastjeff57]

Thanks. I guess a little loose is best for racing.

Jeff

[Fast Fred]

factory is about .004 on cast pistons, a forged piston is going to grow more than the cast bullet when at running temp, so more clearance is needed, about .008

[Fastjeff57]

Thanks!

Happy Thanksgiving to all!

Jeff