exhuast upgrade?

[bordsmnj]

well, i'm thinking that a new pair of custom lightning headers(through transom) will help out in the torque and hp of my new(60 hours) Merc 6.2. i'm also considering others like imco manifolds and risers and i'm wondering what the difference in performance would be between headers
or the manifold dealeos. also i'd like to find out if anyone has actualy done this type of upgrade and if they saw enough gain to justify the cash. if anyone has numbers to share(especially with the no manifold headers)i'd sure like to read all about it. oh, and the lightnings are also water cooled.
has there ever been a test article writen on this sudject to where they took an engine and bolted on the different names and listed performance numbers in comparison? I appreciate any help and or info y'all can give. thanks guys and have a good one -Jas
[ August 07, 2003, 11:43 PM: Message edited by: bordsmnj ]

[Dennis Moore]

I have installed IMCO exhaust manifolds on many small blocks and the gains are there but not as impressive as when installing them on a big block.
The small block isn't as restricted by the Mercruiser manifolds as much as the big block. Do the modification to the exhaust sytem but don't expect a big difference (maybe 2 mph difference). I would guess that the headers will be a little better than the manifolds.
Sincerely
Dennis Moore

[XTRM22]

I changed from thru drive to thru hull on my 19' Galaxie, w/ carbed 350 mag. I used Imco powerflows and saw virtually no difference. It looked and sounded cool, and it did lighten up the feel, but I saw no improvement on mph. Now it is also possible that that hull was up against the wall at 58mph and nothing was going to improve it, a better hull might have responded to the hp upgrades.
My .02
Chuck

[kevnmcd]

Dennis Moore:
I have installed IMCO exhaust manifolds on many small blocks and the gains are there but not as impressive as when installing them on a big block.
The small block isn't as restricted by the Mercruiser manifolds as much as the big block. Do the modification to the exhaust sytem but don't expect a big difference (maybe 2 mph difference). I would guess that the headers will be a little better than the manifolds.
Sincerely
Dennis Moore Dennis - In your opinion which exhaust setup gives you the most bang for the buck over stock manifolds on a 502 MPI? Thanks.

[gnarley]

Here we go again, wouldn't it be nice to get REAL data on any of the different exhaust systems that are available? It seems that no one is willing to put their money where their mouths are & post before & after dyno numbers & performance testing data in a boat.
Why can't Hot Boat do what other performance mags do? It seems like car mags will do actual buildups, do dyno tests & then drive them for real performance evaluations & compare the before & after.
Come on Hot Boat, do a test on exhaust systems. Test one a month & post the test data & test them in the same boat with the same engine. With all the different exhaust systems available this could be a monthly topic & buildup for many months if not longer & sell many more copies of the magazine

[bordsmnj]

thanks Dennis. if it helped a little outa the hole and two mph top end, that would be fine. i was thinking of getting a bigger,less restrictive spark arrester and maybe re map the chip if neccesary.that would probably give me the 70 mph i'm trying for. probably be a month before i take the boat to be fitted for lightnings but i'll post my results when finnished.
Ditto what Gnarly said about the testing maybe they could do sbc and bbc.

[Craig]

gnarley, Hot Boat did do just such a test in the mid 90's as I recall. They tested a set of IMCO's, Lightnings (or maybe they were CMI) and maybe Gil. I'll have to see if I can did up the article.
Craig
[ August 08, 2003, 11:42 AM: Message edited by: Craig ]

[Thunderbutt]

Craig:
gnarley, Hot Boat did do just such a test in the mid 90's as I recall. They tested a set of IMCO's, Lightnings (or maybe they were CMI) and maybe Gil. I'll have to see if I can did up the article.
Craig Craig, your right I remember that.
I think it depends on how much air your putting in the motor. If you have a stock motor I don't think it would be worth the $$$. If you have a lot of input and big heads then you need a good output and I think the headers are the way to go. The imco type manifolds are no differant then the stock Merc's.

[Dennis Moore]

Kevin,
The problem with the 502 EFI is that it goes lean with an efficient exhaust system and needs either more fuel pressure or an ECM fix. If you don't want to fool around with those things then the IMCO manifolds will give you a performance increase without leaning out the engine.
Many people may disagree but the Gil Manifolds are my favorite. The guy who designed them took into consideration the firing order relating to the exhaust system (but they are so efficient that they lean out the EFI).
Dennis Moore

[gnarley]

Ok, so Dennis, Craig or anyone else, can you post any real numbers? I would love to see what the difference is between the Gil's and stock. Due to lack of funds I can't put anything into my deal for a while but if I knew which manifolds performed the best & how much of an increase to expect I would start preparing if there was enough return on the investment.