CMI switch from IMCO cast Header?
 

I want to switch to CMI Big Tube Headers but have several questions? Need aswers fast since a freind of mine is offering me a great deal on some brand new ones if I buy them now.

Boat has 540 cu Blower Motor that puts out just north of 900hp and 890 Torque. Currently have IMCO Cast Header (powerflow I believe) with 4" Tail pipes. The CMI's he has are Big Tubes with 2.375 Primaries and 4.5" Secondaries.

Have been told by several people that my current Headers are way too small for my engines and to upgrade! Should I be going with the larger CMI's (2.375 and 4.5") or the smaller (2.125/2.250 and 4")? Any opinion on what type of speed/power I might gain.

Thanks in advance for any comments or suggestions.

Probably 20-30lbs of toruqe and maybe 1-2mph, but not much. What you will see is that boost will drop 1-2psi, which lets you put some more boost, and more power. Those Imcos are a touch small for your power, but the SC is the power maker, so if it doesn't push more air in, it's hard for it to make any more power. The only difference is lower boost allows less heat, power consumption, etc so you'll net some gain. If you can change pulleys, then you should be able to get 3-5mph easily.

When I look up the specifications on the IMCO power flow they do not call out a specific size for primary? I assume since it it not a round port? How can you compare the actual performance or flow rate of each?

Any other opinions or suggestions will be great!

If anyone has an alternative Header that they would recomment, that would be great also.

Which CMI model header are you talking about and what size pipes?

I am sure Dustin would know the best configuration and size as he is one of the really knowledgable "Puffer Professors"

Best Regards,
Ray @ Raylar