Well first off the 307 piston is not a 4in bore It is the same as our L6 3.875 bore But yes they could very well be .125 over.
Unless they were a custom order they should have a 4 valve releaf
in the tops. Now depending on the piston head thickness, You could mill the 4 releafs into one dish. As to the CCs on the
your right about that.ONLY if the head hasn't been mill.So depending on if it was milled and as to how much was milled off
the CCs may very well be less.
Now for what I see in the photos All that was done to that head is the Boss was removed that was it. No Porting was done
The Valve area wasn't even blended in.
Reason I say this is because you can see the cut line from the
valve job and you can still see the ruff casting in the port.
so from that if i had to take a guess i would say the Valve guide
bosses were not touched either.
So now my 2cent input is this. Pull the head check the CCs
finish the port work. Unshroud the valves Espcaily if it has
a 1.94 intake this will help gain a few CCs back in the head
and also help the air flow. You could also add the bolt-in lump
Which again will Increase the over all CFMs of the head.Then I'd
take a close look at the pistons and see if they could be dished
That way you can still keep the Zero deck,If that is what it is at. And cam wise look for something in the 450-550 range,
and a small 4b carb.
And if it was estimated 350-375hp why did they stay with a
stock dampener??? even though you are plaining a cam change
I would change the valve springs. Because if the valve train
loaded that whole time the springs could very well be weak now
from sitting under a load.
(meaning rockers holding any valves open)
hope my 2cents helps
God doesn't like ugly.
