Piston to wall clearance question

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

Quote:

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Originally Posted by 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

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if pistons are stock you add 030 to original bore size

Quote:

---

Originally Posted by 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

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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

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

Jeff

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

Thanks!

Happy Thanksgiving to all!

Jeff