I need to refer those types of questions to my mechanic, installer Jaime @ Lakeside Restorations I am not too much of a motor head, what I do know is this headers have been dynoed and they produced 40-50 hp., according to Jaime. Sorry I can not help you, maybe Jaime will chime in.

Undertaker

PS As a side note I am thinking about reprogramming the computer at a later date, Jaime will also do that...

While the factory system on its own is not bad, it still is not as good as it can be.. The DMP exhaust has long internal runners, and has runners that carry into the risers. There after exiting thru a venturi they call a vortex. The venturi helps to speed up the exiting exhaust more than many collectors in headers. This also helps to draw in more air fuel mixture into the engine. This requires an adjustable fuel pressure regulator to enrich the fuel delivery slightly. That's how the power is gained with this system.

In reference to Ray @ Raylar he has dynoed the engines with these kits & he has substantiated these gains & the need for the fuel pressure regulator on the Mag Ho applications with the modular fuel pump system.. We are a dealer/installer for his products as well. I have personally talked to him about these systems. Unless I misunderstood Ray, then even though many of the engines you see in his ads have CMI, he said that the DMP systems also compliment his products nicley..

BTW: Ray has if my memory serves me correctly said that the factory exhaust was good for a merc stock part. However Ray himself was able to improve upon it & used to offer that service at one time. He felt that the DMP was superior to doing that, especially with the manifolds going back to cast iron.

As far as the cheapest bangs for the buck, this is one of them..

I hope this helps to shed some more light on the subject for you guys. :)

Jamie / Lakeside

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I am beginning to think a PCM re-program is really needed too. But, all the guys who sell and install headers and or new manifolds say the HP gains are real. I dont want to loose the 87 octane friendlyness anything else. I had the stock PCM on my 6.0HO truck motor reprogrammed for no TM, and premium gas.....thing spark knocks(but does make great power)like crazy w/o the best gas in it so I ended up just putting the OEM computer back in. it was hard and costly to get the exact timing down.

If anything, loseing the 80lbs of iron in the back will help my slug get on plane.

An ecm reflash is not required to run this exhaust. But again depending on the model an adjustable Fuel psi regulator is. The average Psi increase on those applications is about 3#'s..

As far as reflashing an ecm on its own, it is hard to gain much of anything beyond the stock program. It can however add more power when complimenting certain other upgrades. Things like cams, heads, intakes, compression upgrades adding some forced induction systems. What the Ecm reflash does is allow everything to play nicley with each other when major mods are made. That being said I am not saying with an exhaust & a reflash that you wont gain anything power wise, I just am saying the exhaust upgrade will make the most difference between the 2 .. Because the reflash is not required the ecm will just be more of an "enhancer" to the system.. :)

Compared to reflashing auto ecm's, The marine ecm's are already dialed in quite well for a stock set up or a set up with minor alterations. Dont forget some of the power you "feel" in an auto application comes from also tuning shift points. You dont have shift points in the marine applications. Also the auto applications have more emission concerns to deal with on the factory flash. Therefore there is more to gain by reflashing them & reducing some of the emissions programming that is loaded in.

:) Jamie / Lakeside


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Yes the weight reduction is a nice bonus for the people currently with the cast iron manifolds.. :) Jamie

Thank You....kind sir.....

No problemo.. :) Jamie / Lakeside

Thanks for the info Donz33. Having the runners going into the risers and turning and vortex........ interesting. I don't doubt any hp gains from any aftermarket manifolds, I am just skeptical of any real gains. I think I better understand the effects of the header, or header like such as these Dana manifolds. Then again I don't know anything about airflow......

I thought that adding headers and their scavegenging effect would lean out the motor to be just about right because of being so rich on the top end from the factory. If these manifold require an increase in fuel pressure, are they producing more hp than a header.

Thanks,
Bill

No problem.. :) Jamie / Lakeside