454/420 with 496 manifolds????
#1
Registered
Thread Starter
![Default](/forums/images/icons/icon1.gif)
A friend of mine has older 454's built to 420 specs. He currently has the stock merc center riser iron manifolds. Would going to a set of new style 496 aluminum manifolds be worth some HP over the old style iron ones?
#5
Registered
![Default](/forums/images/icons/icon1.gif)
Would the 496 exhaust bolt up to the old style 454/502 rectangular port heads? I thought there were issue with the bolt pattern. Had to redrill stock CMIs to get them to fit a new 496? Something like that?
Last edited by Pismo10; 04-22-2008 at 05:48 AM.
#7
Registered
![Default](/forums/images/icons/icon1.gif)
Also, I believe you are correct about replacing the stock cast iron Merc exhaust with a better free flowing exhaust....especially if you've added a hotter cam. Your engines should respond with some kick...especially in the midrange and maybe 1-2mph on top as Griff said.