I've read that using aluminum manifolds and risers from a 496 on a 454 will improve the exhaust and HP, but how much? Is it worth finding a used set for $300-500 to put on my 454? What will I see for gains and I'm assuming I would have to go up in prop pitch? Is it a direct bolt on? I have a 1998 454/330hp now. Thanks!

The 2001-thru 2005 496 exhaust manifolds are aluminum base and stainless riser, the 2006 thru current are cast iron base with stainless upper. They will both work better than your 454 stock Merc exhausts and I would guess maybe 10 -15 hp more in your stock application. even really good headers or header manifolds are not going to add more than about 20-25 hp at the most on a stock 454. They certainly look better and getting rid of the wet riser joint stock manifolds and their extra weight can't hurt either.

Regards,
Ray @ Raylar

stay away from the 2001 and 2002 alum maniflolds....they have the dreaded "water rail". The water rails rot out first and merc gets 180 to replace them.

I have a pair of cast iron w/ stainless riser take offs I could make you a deal on. Let me know

Brian

You won't have to go up in prop pitch. Its not that much of an increase in power.

The 496 manifold do noe line up with engine like the stock 454ones do. They have a differant angle and stay away from the stock ss risers merc used on the 454 they worp and leak thats wy merc doesnt make them any more. Give me a call if you need help. 281-326-4800