Restriction of exhaust manifold - how much HP
 

Hi guys, I started tearing down the 509SC yesterday (finally...) and started thinking about the exhaust manifold and pipe. (wonder why... Alberts GenIII and 5" pipes are going to be almost too mean looking! :))

Does anyone know how much HP these Mercruiser manifolds with the 4" pipes (I assume the manifolds are made by GIL) can take and what difference a CMI or S-M Gen II or III would do.

The engine is supposed to produce about 700HP@5700rpm

Thanks,
Tomas

Re: Restriction of exhaust manifold - how much HP
 

I believe you'll gain about 30/40 HP with CMI's. I can get you a great price to help offset the shipping costs. :D

Albert is very pleased with his exhaust and will probably chime in soon.

Re: Restriction of exhaust manifold - how much HP
 

I can tell you that I saw no power gains going from the stock Merc/Gils to a set CMI Unitops on my 525SC. It could be that power gains will not be realized until you get into bigger HP, like what you have.

Re: Restriction of exhaust manifold - how much HP
 

When I, last spring, talked to the guy that built the engine (Dave @ MDG Performance) his advice was to replace the manifolds with some good headers, altough the SM Gen's is of course also an option.

Re: Restriction of exhaust manifold - how much HP
 

Tomas, the Gills you have there are very good to a certain point. However, with your kind of power I beleive an investment in a quality set of exhaust will let your blower release the air faster.

Re: Restriction of exhaust manifold - how much HP
 

Yes I can see that, for what kind of power are the Gil's good?

Anyone now of some used, good condition Gen III's?!:rolleyes:

Re: Restriction of exhaust manifold - how much HP
 

I have a pair of Gen 3`s for sale complete, will seperate $1800.00 each pair.

Re: Restriction of exhaust manifold - how much HP
 

4,5 or 5"? Complete with manifold and riser/collector?! I assume it's $1800 per pair and you have two pairs?

If you don't want to post pics here then could you please send them to [email protected]? Thanks!

Re: Restriction of exhaust manifold - how much HP
 

5 inch tails, I`ll get some pics this week for you!!!!!

Re: Restriction of exhaust manifold - how much HP
 

Gem 3 SM only way for a blower motor...any thing else is a 2nd best