496 CMI Headers
 

Anyone think that the new 496 CMI headers would add any performance to my motor package or not ???

496mag HO 3.3 Whipple 8lb boost 830hp

Think I would get the 60 more horsepower CMI is claiming ?

Re: 496 CMI Headers
 

You run 8# boost on a 496HO?????????? :eek: :eek: :eek: :eek: :eek:

I really hope you don't have the stock pistons in there. If you do, they won't be in there for long.

Re: 496 CMI Headers
 

a-men

Re: 496 CMI Headers
 

Why are you so worried about 8lbs of boost on a 496 ?

Re: 496 CMI Headers
 

Ok tell us the goodies, how many hours and whats inside.

Re: 496 CMI Headers
 

LOL... Ok, Ok...

This motor has been alot of work and alot of money. Not just the parts and build money but the time and effort involved expense as well.

These motors have been a combined effort by Dustin at Whipple and Larry Peto in Tucson, AZ.

Fresno (Dustin), Tucson (Larry), Anaheim (Me). There is now a permanent groove in the roads between these three desinations.

This is motor is 1 of 2 496's that I have had built. This one with the 3.3 Whipple and I the other with a 2.3 Whipple.

The 3.3 has all new internals, ported & polished heads, custom JE blower pistons, Whipple programmed computer(hours and hours spent by Dustin), larger heat exchanger(not pictured), 14qt Dooley oil pan, Etc. all of the best parts. It runs 830hp with 8lbs of boost and 753hp with 6lbs of boost. This motor has about 10 hours time on it in the boat.

The 2.3 has all new internals, custom JE blower pistons, Whipple programmed computer, Crane rollers, Scat, Etc. once again all of the best parts. It runs 640hp with 6 1/2lbs of boost. This motor has only dyno time on it and happens to be FOR SALE.

Now I just can't wait for summer...

Re: 496 CMI Headers
 

Long primary headers on blown applications do not show the same proportional gains as on a N.A. engine. Many Merc 1075's use the Big E-top header for function or the long tube race style header for a little more show.

Re: 496 CMI Headers
 

So does anyone have somewhat of an answer to my question?

Re: 496 CMI Headers
 

The answer to your question is yes they will help, but you might not see the same % gaines that none supercharged motors get. Naturaly asperated engines need more help to rid the exhaust, whereas, forced induction helps push the exhaust gases through (depending on came overlap). I run CMI's on my SC motor, wouldn't go without. And they really look great too.

Re: 496 CMI Headers
 

Thanks for your reply, and yes they do look good as well...

Re: 496 CMI Headers
 

i think i would look at the eddie marine emi exhaust for that application first.. it doesn't have the choke points that stock manifolds have so it should help flow. but your not paying double for those long runners that aren't going to help that much. although the photos' look like the risers are different from stock.
Don

Re: 496 CMI Headers
 

Cmi makes excellent 4 tube stainless headers and they can add power 30-50Hp to almost any high performance BBC marine engine with proper application.. The type of header you run with supercharging is not as critical as it is with a N/A motor. If it were my boat and motor I would look at the Stainless Marine High Torque Three, CMI Etops, or Dana Marine Manifolds with big tube collector riser. These units have larger volume risers and should work as good as it gets for supercharger exhaust blowdown. They are also significantly less expensive than long tube stainless units.

My two cents.

Ray @ Raylar

Re: 496 CMI Headers
 

Ok, call me stupid but will they fit ?

I thought (cause I don't know) the 496 kit was the only ones that would fit.

Re: 496 CMI Headers
 

Betitbig:

I would measure from the top of your existing stock exhaust risers up to the bottom of your closed hatch. Thats how much top clearance you have if any. Then measure from the top of these stock risers down to the level of a line running through bolts that bolt the manifold to the cylinder head. This dimension can then be checked by any header or manifold supplier against their dimension and tell you if those headers or manifolds will fit. "Measure twice, cut Once!"

Ray @ Raylar

Re: 496 CMI Headers
 

I will be on the dino in a week or so.I also have the same cam as you ,same computer program and 3.3 comp .We 708 hp 8#s boost with 2.3 compressor.Tyler Crockets doing my work now. and we will dino with stock and cmi,s also.Tyler also said etops would work the best I,ve been following your engine biuld thru Larry and Dustin. Those are some great no.s what size pulleys are you using.

Re: 496 CMI Headers
 

Hey Robert, how are you doing...

I am happy with the numbers so far, now to just get it in back in the water again. I am now looking at the CMI e-tops because as you know, good is never good enough.

Im going to Larry's this Monday to pick up the boat and spare (for sale) 2.3 motor. The 2.3 made 640hp with 6 1/2lbs of boost, with dyno time only so far, and hopefully some will want to pick it up.

Re: 496 CMI Headers
 

One of the most important factors which you should consider with the CMI's is your cylinder temp should run a litte cooler for sure than those stock manifolds. Thanks Cam-shaft.

Re: 496 CMI Headers
 

Go with Stainless Marine Gen III for the supercharged engines. They have been proven to provide more power and torque over the headers.