Have em mill about .040" and slap em on.

 

0.007" milled=1cc lower

 

I have had .045" cut off of some gen 3 heads with no intake problems at all.

 

Why ruin a set of 243's for 15 rwhp???

 

He'll gain compression and flow, both will compliment the cam well. Thats not ruining the heads imo, if he got a deal on em i say use em. And if he knocks the hump out of the intake ports he'll gain more than that.

 

You would only need to mill them 0.023” to get back to the stock 61.15cc from the 64.45cc of the 243 heads. You could go ahead and mill them about 0.031 to get them down to 60cc and shouldn’t present any issues.

For nice round numbers, I would say either cut them 0.025” to get back close to stock or cut them 0.030” for a slight bump in compression. That with the better ports and larger intake valves should net a slight improvement. If you can get the heads for a reasonable price and don’t mind the work, why not do it?