Headers & Horse Power

[Lightning]

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 will add to the equation?

[Havasu Carrera]

I guerantee a higher comp piston and a cam change is good for atleast 100 hp. Your exhaust is a gueranteed restrictor. (kinda like restrictor plate racing only by pluggin the exh. Since your motors done you would be silly to run the old manifolds. Surely I'm not gettin flamed with this help. Night folks.

[WannabeRacing]

Lots of variables. What you have now, to what type of headers? You get a tuned merge collector header on a spread port engine and it will make as much as 20 over a standard good tuned header. Maybe 35-40 over an untuned header.
You will make more power, but just how much is open to debate and what header you go to.

[jbone]

On my stock ZZ502, I picked up 250 rpm on my 21 ft jet when I went to Lightning thru transom headers. That is about 50 hp.
J

[centerhill condor]

the nice thing about increasing the exhaust system is that it doesn't adversely affect reliability. You bought the bread now get the butter! It would look better also.