Originally Posted by streetmaster42
Point well taken
The S/R 76cc heads i bought could only be milled a total of .021 which was on the spread sheet that came with the heads. I had them milled .007 because they needed cleaned up, yes they where whorped. So if i do anything i'll just get another set of bare castings with 67cc chambers, and have them ported.
If you are going to spend the money to get another set of heads get a head that flows the numbers you want. You can mill a S/R head down to the intake valve seat edge and or the spark plug hole boss. Which ever comes first. That is the physical flat mill limit. Should be able to get to 69cc with that.
"and have them ported
" Porting S/R cast iron heads is time consuming and labour cost prohibitive.
These heads, like most stock heads are not worth paying someone else to port them. Its a do it your self thing
or else its just not cost effective.
Unless you do the porting yourself
and pay some one just whats required to finish them up with required machine work, its cheaper and more cost effective to just buy a aftermarket head that flows the numbers you want.