When you want to know what the chamber volume is for your heads........ you check them.

This is just engine building 101.

I recently had two sets of brand new TF270’s in the shop. The chambers are CNC machined. The chamber volume spec is 78cc.

On one set the chambers were 78cc......... the other set was 76cc.

I hear of people checking 516 heads that are well under 80cc.

I’ve never seen an uncut set under 81cc........ and have seen a few at closer to 84.

You check them........ they are what they are.