Have a 2002 292 Formula Fastech looking to convert 6.2 liter motors [320 HP] to 400 HP natural asperated without headers. Then adding CMI headers. Does any know the HP gain with CMI headers? Also has anyone done this - looking to know performance and top speed [with what pitch prop]?

JC Performance just made 450hp out of my 350 mag mpi's I even kept the fuel injection give him a call.

Ahh yes the debate begins. Website and ads claim 25-40 HP...realistic, nothing. Many have spent big money thinking it will net big gains just to be disappointed. The bigger gains will be noticed on larger highly modified engines that require them. I would save the money and save for gas or buy a less expensive manifold style for much less money unless you just want the bling....then go for it.

You will only pick up HP if the engine needs to breath more.On a stock 6.2 you will gain nothing.Unless you go with higher compression,cam etc.Which will probably mean new rods and maybe a crank.

The 292s will plain faster with aluminum manifolds as it takes like 250 lbs of the rear of the boat.I did that and its a world of difference even in how it rides.

What was done?

Running Stainless Marine on my 6.2 just had it Whippled along with cam and head swap mines making 595 HP and 570 ft. Lbs of torque.

Everything! Aluminum Edlebrock heads, je pistons, rods, custom cam, etc. I was real happy with the power & tq I cant have you pass me this year at the Blackjack Poker Run.

Thanks all!!!!!! - Expensive Date you indicated that made big difference on plan [which makes sense due to the weight - my first thought is once someone else is end their that will make the same, but not really do to leverage all the way in the back?] and handles. What is the difference you noticed in handling? Hopefully for the better :-)? I am assuming not much to top end speed after doing that [since didn't really say much about that]? If you had to redo would you do it again [I know the 292 does take awhile for plane so that alone maybe worth it]? I know I race a 271 with 350 hp motors I will have him at top speed slightly [about 67 mph on gps - 72 mph on speedo], but out of the hole he is approx 50 yard in front of me - since it takes about 11 seconds to get on plane.

Power gain of the CMI headers does not really matter. You are going need some type of performance exhaust to prevent reversion.