Is this because of the other things that you have done? Or is your engine special?

Just looked at the DOA website. They are claiming 33hp by simply porting the heads with stock exhaust. That is a big gain if the exhaust is the limiting factor. If it were then they would not see a 22% increase in power with stock exhaust.

I wonder what it would do with the bigger valves?

DOA is claiming 225hp out of their longblock. I can only assume that this means that I am bolting stock everything else onto it. That is rule of thumb for crate motors unless they specify carb size and headers etc.

I am going to look up some headers and see what they claim for hp increses.