I have a 496HO and I am looking to upgrade my horsepower a little, I want to know about roller rockers (what brand) and then I want to add stainless custom marine headers and probably custom ecm caliberating by whipple any thoughts on this. Is there a differnce between the k&n filter and whipples billet custom flame arrestor, if so what one is better.

Roller rockers will be good for 0 HP, ok, maybe 1 or 2hp.
You don't really need them. The need for them is mostly determined by the cam profile.

As for the other mods, I don't know what your actual gains would be, but I would say minimal, if any. Best case, you might see 2mph.

well, where to start, With the 496 I would recommend draining some of your coolent, mecury came out and said those engines are running a little cool, it will performe much better running hotter. the recommend draining about 1/2 of your coolent. also a little bird at merc told me to spin that moter at 6100 rpms for optimum performance, they way low balled there #'s, this means you will have to lab your prop and probobly pitch down. another little trick that i have learned about going faster is that all that heavy greece in the drive creates alot of friction and slows you down. get rid of it and replace it with regular motor oil, merc recommends 5w-30. doing these things you should gain about 9 mph.

And what color is the sky in your world?

Good advise Hugetime!

But SERIOUSLY.... I have the 496HO and wouldn't modify it for the gains you are looking for. I have done a lot of research. Like Griff says, maybe 2 mph with an exhaust change. You will gain nothing changing the filter.

If anything, I would spend the bucks for a blower and gain 10 - 15 mph. You have to ask youself if it's really worth it. It's a dead reliable, idle forever, run wide open forever motor as is. Why mess with it?

hugetime1's post would be considered a joke.

He forgot to use a

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Do you think a cam and rockers along with exhaust would help or not.

Well that explains that