I agree. So, do you or anyone on here know of and are willing to share how to port the stock 496 headers for more flow? I have plenty of time this winter to do a ton of hand work...

I believe Raylar was in the process of developing an exchange program for your stock manifolds for his ported ones...

not worth much tho...10-15 hp?

Run a search and you'll find results from end users.......

......have been running them for several weeks with what I would consider fairly good results. I am running a Velocity 290, with a Bravo 1 labbed 28. Started at @ 4900 RPM, 72-73 on spedo. I am now at @5150, 76-77 on spedo, but running out of prop at times. Tried a Bravo 1 labbed 30, but it was a bit too much prop. Ran close to 4900 RPM, but speed was not there. That prop is being worked on now to hopefully allow me to run at 5050, and perhaps gain another MPH or so. Velocity hulls react very well to minimal power, so other hulls may not see the same results. If I maintain a consistent 4, I will be satisfied. I always run above half full on fuel, so that is not an issue.

.....Results are in on the 496 CMIs, 482hp with no other mods. Sounds good. See latest Powerboat Mag

well if we all went by speedo #'s I wouldnt need these headers...

The part about Velocity's bottom responding very well to power(among the best) is certianly true. Owned 2.

like I said earlier, single engine fast bottoms/lighter boats seem to be the ones getting the gains for the $$.

So you guys have it made at 1K per MPH.

Point me in the direction of documented results on 9-10 thousand pound twin boats.



57 HP? That's a new high quote.

Again Dyno...CMI buy a big ad in PB this month?

Just kidding!

I'm not busting vendor's balls...

CMI's for pricing is more to the point, price 'em like (and make them in satin) satin elbow tops and they'll sell like hotcakes.

no one's guinnepigging them on heavy twins.

Give me a couple pair. After 200+ hours on my 353 I know where my boat stands in terms of performance. I'll report accurately and scientifically.

Then I'd just need another winter project to keep me busy! The power gain isn't the point...it's the time in my shop that really makes it a worth while endevor. Far cheaper than visiting a shrink!

Somebody has the specs. on the DIY manifold porting, ask 26Sonic from the board, I think he knows who has the blue-print..

Guys, let's be realistic. They are worth some performance gains. Maybe not as much as billet throttles, colored bezels, mirrored hatches or any of the thousands of other parts we spend a ton of $$ on and install on our boats for that little something extra.

CMI makes a great performing and looking product that may not be for everyone or everyone's budget. Do they enhance the performance of the engine? Yes. Is going to get you into the record books with stock power? Probably not. Do they perform and look cool - YES!!