friends 318 build

Stroked 340, there is a formula for this, I got it from my bible, The Auto Math Handbook.

It's based on 'displacement ratio' which is cyl. volume divided by chamber volume and is always one point less than comp. ratio. So for example, if you have 9.5:1 comp ratio, your 'displacement ratio' will be 8.5:1

Clearly you'll need to have a new target disp. ratio and would also need the original comp. ratio to figure it out.


new disp. ratio - old disp. ratio
________________________ x stroke

new disp. ratio x old disp. ratio


I did a quick calc. using theoretical ratios of 10.25 and 8.5 for the old. I came up with . 066" to mill. Seems like a lot, but that's a 2.25 point jump.

I'll guess he's going to run 13.2.

Hope that helps.