502-415 HP MPI Exhaust Manifolds
 

I am planning on replacing my stock cast iron manifolds for aftermarket manifolds. i am looking at making the change in terms of preventive, but if I get a little better performance, I won't complain. I don't have any unrealistic expectations of bolting on 10 MPH!! i would like to hear results others have had with the different brands on the market, completeness of the product, and quality.

I am not interested in CMI, or Lightning, tube type headers. nice, but just not in the cards with the stock set-up.

Re: 502-415 HP MPI Exhaust Manifolds
 

I had a single engine bb in heavy deep v; 1st added CMIs (very basics ones)- I picked up about 1-2 mph, then was able to afford the head work, cam, intake and picked up another 5. Loved the 'ripping canvas' sound at wot- put on shotguns mufflers and softened the noise.
Sold the boat earlier this year and after 10+ years the CMI's were performing well with no problems and shinning bright.

Picked up a twin engine heavy deepV early this year and added IMCO powerflow and using my stock speedo, I believe I picked up (roughly) about 2 mph- but very hard to judge because it was before in salt and now in fresh still picked up 2.

Don't rule out the CMI's because of price-great true header (IMO) for a very reasonable price if you deal with some OSO members like Fred at Trick, Teague etc.

My IMCOs, very happy so far, IMCO service has been very good for me-had minor issue and dealt with Fred directly and he stepped up to the plate and offered very good support.

Good luck

Re: 502-415 HP MPI Exhaust Manifolds
 

Hey 32storm,

I have a pair of Stainless marine exhaust on my Sonic and they are great, I have noticed a 2 mph gain with the change. The weight alone would suprise you. My moters also run a little cooler since the change...

Jimi

Re: 502-415 HP MPI Exhaust Manifolds
 

The EMI's are a pretty good value for the buck. They look decent too, you can get them in a ton of different colors as well as polished.

Re: 502-415 HP MPI Exhaust Manifolds
 

Another vote for Stainless Marine.

Re: 502-415 HP MPI Exhaust Manifolds
 

I had the same engine in a 26' scarab. took it out and ran it on the dyno, it made 420 hp. Removed the fuel injection and put on an intake and carb, and stainless marine exhaust and it made 468 hp on the dyno......boat went from 63 mph to 68 mph......

Re: 502-415 HP MPI Exhaust Manifolds
 

another vote S/M mine are 11yrs old always in salt water, but I do flush them after

Re: 502-415 HP MPI Exhaust Manifolds
 

For durability, the Stainless Marine exhaust are the ticket.
Airtime's 11 year old manifolds are a testament to their longevity.
I personally like the riser to manifold connection. Makes it very easy to remove if you want to check for reversion telltales.

Re: 502-415 HP MPI Exhaust Manifolds
 

Yes, Stainless Marine...
+200rpm on my engine... :D

Re: 502-415 HP MPI Exhaust Manifolds
 

When I repowered with my 502 (415 hp), I put the Stainless Marine's on and they have been great. Never run them with any other exhaust so I can't sany anything about improved performance.

Dail