If that is the case I'd have them knurled and touch up the seats.
The promaxx cnc head is still cast iron. Just a new iron casting.Pump gas compression with the change to aluminum? I'm building a motor for my 4x4 daily, currently to come out around 8.8 SCR and 7.2 DCR, but between the machine shop cost for studs, oversize valve seats, new guides, etc, I'm thinking about changing to the aluminum head. Seems like in the V8 world, iron vs aluminum is worth about 1 in compression? Anyone have the new promaxx running, or guesses on what DCR the aluminum 300 will handle on pump gas? Seems like changing to flat pistons (I'd much rather keep my 519P's) would be too much compression without a monster cam, but maybe there's enough casting to deck the aluminum head a bit for 9+ SCR, and get a bump over iron with the 25cc pistons and cam I already have?
And add to that, aftermarket manufacturers tend to make their products from aluminum because:I think there is a slight misconception about aluminum heads.
It's not that with an aluminum head you can use a higher compression ratio.
It is more that with an aluminum head you will need to run a compression ratio about one point higher to achieve the same thermal efficiency as an iron head. Because the aluminum head absorbs more thermal energy (into the coolant system) it will be less prone to detonate. It will also be less efficient at the same compression ratio.