CMI Headers/496 HO
 

Looking to purchase and needing some feedback. What kind of HP gains and sound over stock? Advertised seeing a 55 Hp gain? Worth the money or not?

Re: CMI Headers/496 HO
 

We recently installed a set of CMI Headers onto a 35 Outlaw, twin 496. Fairly straightforward installation, but still a pretty big job. We had a few issues with some fitment (due to keeping the Quick and Quiet diverters), but CMI was great about getting us the parts and help we needed.

When finished, the motors looked great, and ran noticeably better.

Did we get a 50+hp gain? Hard to say, but I doubt it. The boat is noticeably quicker, but top speed is no more than 1 or 2 mph higher.

Is this a worthwhile modification? Yes. The cool factor is way up there - sound and looks are a lot of boating, and these have both to the max.

-David
THUNDER MARINE
727-501-3183

Re: CMI Headers/496 HO
 

Thanks David!

Looking to install in a 28' Advantage Victory. I have been told they are worth the sound and HP gain of a 525 at fraction of the cost?

Re: CMI Headers/496 HO
 

Did you take any pics of the final product?

Re: CMI Headers/496 HO
 

Great sound and looks, and some moderate HP gains have been reported. Do a search; there are several threads. Fred at www.trickmarine.net has sold a lot of sets to OSO members. He can give you a rundown of feedback he has been given.

Your 496HO is making 425HP+/-. The 525EFI is making at least 525HP, and many are dynoed out of the box at 535-540. If you get your CMI headers installed, you MIGHT get up to 470ish HP out of your 496HO. A 35HP gain is more realistic with a little aged 496HO.

The older 500EFI was rated at 512HP at the crankshaft and 470 at the propshaft. Expect your typical Bravo1(any) drive to eat 25-50HP, so you can figure out your propshaft HP. Adding headers to a 496 does not make a blue motor, but it should net you some gains. (Although there are a few folks that I know whom have upgraded, who have not gained anything.)

Its also worth doing a search on "Raylar". He has forgotten more info on the 496 motors than most of us know. He has a lot of products to give the 496 some pep.

Also, this section is for asking questions about how the forum works, and issues. Your question is of a technical nature; and belongs in the Technical area of the Forum found here:

http://www.offshoreonly.com/forums/f...splay.php?f=20

Re: CMI Headers/496 HO
 

The average speed increase reported back to me has been in the 3 to 4 mph range. The majority of the sets sold have been without the Corsa kit.

Re: CMI Headers/496 HO
 

I put a set on my miserable old tub that are only the e tops, not the kit you are looking at. I did the prop and bottom paint at the same time and made 11 MPH!!! I personally think that it is the best money you can spend. I would buy these things before petrol. They are so good its actually not worth going boating without them. You can run a better cam and do all sorts of up grades you cant do without the CMI headers. The look is worth the money alone. Only my opinion though. Jas

Re: CMI Headers/496 HO
 

Before you do anything pull your "turbulator plates" out (between the manifold, risor). It is good for 10-15 hp. Raylar will verify that for you.
Do a search on this forum for 496 exhaust manifolds and you will find a thread were Ray talks about porting work on the stock manifolds which are actually made by Gill. In a nut shell he says they are not bad for a stock manifold and with some porting work he can really wake them up. I think it also states that he has made up to 550 hp on the stockers with the porting work in conjuction with his kits. If you check out his web page you'll see several of his motors are running the stock manifold only with the paint removed and then polished. They look pretty good. Between the turbulator plates and the porting you could easily see the same 35 hp gain at a fraction of the cost.

Re: CMI Headers/496 HO
 

The 496 Kit is a very reasonably priced upgrade for the increase in performance and of course the "Bling" factor!!

We have several sets in stock for immediate delivery.

Let us know if we can help.

Kirk

Re: CMI Headers/496 HO
 

I can't find the thread which details how to port the 496 exhausts...anyone have the link?