exhaust

[stinger]

Was wondering about a exhaust upgrade for my engines. I was considering the alm 496 manifolds, would there be any trq. or hp gain over stock iron manifolds? I have 496(stroked 454) dart pro 1 310cc alm.heads edelbrock rpm intake,hyd.roller, 750 marine demons with merc. stock wet exhaust with accesseries it dynoed at 600 trq 500 hp. Should I consider aftermarket , or the 496s and what should I expect to gain? thanks

[Griff]

Do you have the stock iron manifolds with short risers???????? What exhaust was they dynoed with?????? That crappy exhaust may be costing you 40+ HP. Anything will be a big improvement.

My choices in order of preference and cost for what you have would be CMI Unitops(about $5000), Revolution marine(about $2500) and then the stock 496 exhaust(about $1000).

[Tomas Wallin]

Do you have the stock iron manifolds with short risers???????? What exhaust was they dynoed with?????? That crappy exhaust may be costing you 40+ HP. Anything will be a big improvement.

At least...

[Chris]

Alot of engine builders/dyno operators either aren't equipped or just don't use marine exhaust when they dyno. Using dyno headers and then sticking Mercruiser log manifolds on the motors pretty much invalidates the test.

[stinger]

We used the stock merc marine manifold 4" dia with 6" risers wet with the sea pump and water pump. We only dynoed it to around 5000, 5200 , but when its running in boat it only gets to 48 4900 . Wonder if its the exhaust holding it back some?

[KEPP]

We used the stock merc marine manifold 4" dia with 6" risers wet with the sea pump and water pump. We only dynoed it to around 5000, 5200 , but when its running in boat it only gets to 48 4900 . Wonder if its the exhaust holding it back some?

You should be able to make great gains by replacing your stock iron manifold with some aftermarket cast aluminum. Not only are you saving the weight the manifolds will help your engine breath a lot better. We have all the popular aftermarket brands, such as Gil Marine, Hardin Marine, IMCO, and Stainless Marine. I can make you a great deal on the some Gil Marine with Hardin Marine stainless risers, let us know if you are interested and good luck.

Thanks,
KEPP

[Griff]

We used the stock merc marine manifold 4" dia with 6" risers wet with the sea pump and water pump. We only dynoed it to around 5000, 5200 , but when its running in boat it only gets to 48 4900 . Wonder if its the exhaust holding it back some?

How its propped is keeping it from getting the rpms that they saw on the dyno. New and better exhaust will add HP to what you have. If they dynoed at 500hp with the iron manifolds, then better exhaust could put it up to maybe 550HP.

[Lakeside]

Budgets aside, Yes a better exhaust will be better for your application. It is also usually one of the more simple things to do. We like to usually use SM, GIL & CMI. The stock set up that you have wont do anything for you , and upgrading to a 496 take off exhaust will only help a little in breathing, but would help more with weight.. Jamie / Lakeside