I'm rebuilding a '83 FXWG. The Cylinders are Zodiac Enterprise "big bore."

I just dropped them off at a local (very reputable) machine shop for honing. I asked them to call me with the bore size when they had a chance to mic. He just called me back with 3.657". We had a short discussion on bore sizes. He assured me that "thirty over" means additional diameter, not cutting thickness. I always thought that it was the other way.

So... it sounds like I have 3-5/8" bored 0.030 over which is 3.625" plus 0.030" for a total diameter of 3.655". (allowing a couple thousandths for hone.

Is that correct? I was always under the impression that "thirty over" meant adding 0.060" to the bore.

I need to order my rings and I would like to have a little higher confidence level.

 

Your local shop is correct...

 

Yep. What hotrodfatboy said. You are .032" over.

 

.030" oversize is what you have.
If .060" o/s, that would have you at 3.685".
Scott

 

Thanks for the confirmation, guys. I've had several engines bored from a KZ-400 to big block V8's and everything between. I guess this is the first time that I've actually determined an existing bore to match rings for. I've had the same misconception the whole time.