I posted this in Gear Head, but thought i would post it here as well...
The setup.... I have a 468 in the boat with Merlin Heads, roller rockers, etc... 9.6:1, Holley 850, stock Marine Power manifolds. The motor was built by Tom Papp - he estimated it to be around 550hp.
Original motor was a Marine Power 454P - 390 hp.
I am considering adding a set of headers, however don't know if it's worth the money. When Tom built my motor, he said that the cam and piston change alone on the same base motor (different customer) as mine showed about 90hp on the dyno.
The question: How much horse power do you think a set of headers (Lightning Headers) will add to the equation?