Does anyone know of a summary of the different Aluminum Exhaust Manifolds available for Marine BBC applications (i.e. Stainless Marine, Eddie Marine, Revolution Marine, Gil...). Would like to see a summary of 1) Performance improvements, 2) Weight reduction, 3) Pruchase price and, 4) Warranty. Also interested in real world experiences with these products. I am looking to replace my cast iron manifolds on twin 502 MPIs and want to maintain the silent choice system.
Thanks.

I bought some Eddie Marine about 6 years ago, they are still on my Velocity. The guy that did my engine swap said he was impressed by the quality considering they were quite a bit less expensive than other brands. At the time, EMI offered "hard anodizing" for corrosion protection on the inside, which I got, but it was extra. not sure now. They did slightly interfere with my power steering hose which had to be modified, but that was easy.

One Word: DANA.

IMHO i would not buy anything but stainless marine Gen 111...they make the most power on the dyno and the come with a warrenty......It may be the last set of exhaust you ever buy.....

On a big-cube blower motor I would agree with Nocigarette on the Stainless Gen III's but that is way too much manifold for what I gather are pretty much stock motors. I replaced my stock Merc manifolds last spring with a set of Danas and am very happy with the results. They took a lot of weight out of the back end and the motor breathes so much better. Mid-range performance is better, which translates to better fuel economy (if there is such a thing on a boat) and I didn't have to modify anything to make them fit. ANY good quality cast aluminum exhaust will be better than stock, but for my money the Dana is the best choice overall for a conservatively built application. Make sure you get a plug read and adjust accordingly because the Danas scavenge better than your average cast manifold. Still not as good as headers, but close enough that the reliability of a solid casting offsets the additional gains (and potential problems) of tubular headers. Without doing a whole lot to it, my old 454 is now running with the 502MPI and 496HO crowd, and doing it on 87 octane. Certainly not the performance level most of the OSO guys strive for, but I'm happy. They look good too.

Might want to read the thread "496 exhaust" with our opinions and real explanations of headers versus just different brands of manifolds for some direction for a 496.
Best Regards,
Ray @ Raylar

Replaced Merc cast iron mans and risers with Stainless Marine and had to readjust the idle speed of the engine. This being the only change so it improved breathing so much it picked up 200 rpm idle speed, honest no other changes at all.

I'm partial to Stainless Marine. I like the variable angle where the manifold meets the riser. The ability to vary the angle (left and right) on one plane might come in handy. When I went to long, through transom risers from short risers, hose and tips, my holes didn't line up perfectly. I just moved the riser a little to hit the hole. You can't do that with most of the others.

Mine are on 502EFI and I consider them a lifetime investment. They are great. Easy on/off.

Eickert has a dyno comparison chart on his site- all the popular manifolds.

FWIW- his are very nice. SM's are too.

I also like Dana's,...........they keep all the primary's separate in the manifold and in the elbow.

Very Nice pieces and well priced.

Pictures are compliments of ( 288sunny & zimm17 )


Jon