CPPerformance

All true high performance applications wether its Mercury, Ilmor, Chief, or Teague for example; ALL use a true tubular style header for maximum performance. That is why at CP Performance we offer 496 headers from Lightning and Hardin Marine.

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Bill 3

Will the Lightning headers work with Corsa diverters?

yesrej

thanks bill.

Bill 3

That's right, you did ask the same question on their other post. Now if we could get them to answer that and what their performance gains were so we could compare them with these others.

Seems that no one has done as much research in to this as Dana has though.

Michael1

Without the baseline dyno figures, the dyno sheets with the headers don't mean a whole lot. For instance, what was the air-fuel ratio on the stock engine compared to the one with the headers and pressure regulator? What were the horsepower gains, if any, at various rpm's? What happens when mufflers are added? What happens when the test is run with a wet exhaust?

Now if you want to buy headers for the bling factor, then no doubt you should do it. There is probably nothing more impressive to add to an engine. If you have an engine with a high overlap cam, and dry exhaust, then you should have them. With a stock engine, with a low overlap cam, wet exhaust, and perhaps muffers, I haven't seen any real supporting data for $3K to $4K headers. I need to see a few tests (for repeatability) at baseline, and with headers added.

Michael

Raylar

I thought i would chime in here because we at Raylar ran all the Dana Exhaust dyno tests and I can assure you we tested both the 496mag and the 496Ho engines for baseline output before we installed the Dana header manifold system on the motors. In both cases the stock untouched motors made within about 5-10 horsepower of their Mercury ratings. after the Dana sytem was installed the engines made between 42 and 48HP more than the baseline tests with a significant increase in torque numbers, also as expected.
Its important to realize that even though the dyno sheets show we were using premium 91 octane fuel the specific gravity measurments of the fuel being used indicated it was closer to 89 octane in reality. why, I am not sure, but our highly oxygenated (alcohol laced) fuel here in Southern California tends to be that way. Its also important to remember that HIGHER OCTANE FUEL DOES NOT MAKE MORE HORSEPOWER! It is simply used to control possible knock in higher performance engines.
If a given engine has higher compression and aggressive timing it may need a higher octane fuel to prevent knock and engine damage from knock. Its the higher compression and timing that add the power not the fuels octane. 496's with their moderate compression ratios and the conservative timing in the Mercury ECM, most fuels of 87octane seem to be adequate to prevent knock, even with our 525HP kits and good exhausts.
Hope this information clarifies a few questions here.

Regards,
Ray @ Raylar

dana marine products

[QUOTE=Michael1;2042673]Without the baseline dyno figures, the dyno sheets with the headers don't mean a whole lot. For instance, what was the air-fuel ratio on the stock engine compared to the one with the headers and pressure regulator? What were the horsepower gains, if any, at various rpm's? What happens when mufflers are added? What happens when the test is run with a wet exhaust?

To re-clarify, the dyno sheets do NOT reflect the engine with the pressure regulator installed, thus the high exhaust temperatures. The air/fuel ratio stock vs. after exhaust install is irrelevant. The bottom line is, look at the dyno sheets, the 496 HO got lean with the exhaust added. Something has to be done to correct that. I think it would be agreed by many, that there is no way Mercury sends their engines down the road with 14.00 air/fuel #'s. The dyno sheet reflects the engine with NO fuel modifications.

The engines do not make near the horsepower or torque stock as they do once our exhaust is installed. As backed up by a non-biased opinion, our systems really work.

Adding mufflers or water would affect the outcome. But it would affect it both ways, it would affect the stock engine just as it would the modified exhaust version. If someone is losing 20HP because of a set of mufflers in their boat, they should look at another muffler brand. I can't regulate what people have in their boat. I can show you what the engines make for hosepower and torque after our exhaust was installed. If anyone is looking for deeper information on what Mercury claims their engines put out, you'll have to call Mercury.

I can assure you, you'll find out exactly what I've already disclosed, the stock engines will make slighly more HP than the stock rating. (by slighly I mean like 5-8 HP difference). On the other hand a 496HO was just dyno'd stock and it only made 417HP. It can go either way. Such is life with a production engine.

tblrklakemo

Thanks guys....just need to be sure that I can run my boat the way I run it with headers. No need for premuim to combat knock, and real HP gains..enough to warrent a bigger prob.

LAKESIDE RESTORATIONS

Tubular headers will allow the exhaust to exit more easily than a stock set of Merc manifolds, and yes there are some headers that provide better scavenging than others. Until now that was the only way to go because manifolds could not quite compare with rare exception.. Just having open flow exhaust on a stock or relativley stock engine is not always going to allow it to perform better. Part of the reason for runners in headers & manifolds with runners is to tune the exhaust & try to create a scavenging effect.. Some headers do it well, some ok & some not at all. The design of the manifolds By DMP is designed to scavenge & it has individual long runners & a vortex (venturi) built into the riser to aid in the scavenging of the exhaust. This is what helps to quickly remove the exhaust & pull in more air fuel mix..

If memory serves me you guys also have or had some Keith Eikerts that had long runners in aluminum manifold that tried to accomplish similar things at one point for NON 496 applications.

Also not all exhaust systems require cowl modification..

WE have used Hardin / Lightning headers in the past & I dont have anything bad to say about them. As far as headers go they are a good bang for the buck for certain applications. WE have had good results with them on Blown Jet applications..

However I feel the flow torque is currently the best bang for the dollar if you have the space to run a wider manifold on a 496

Jamie / Lakeside

CPPerformance

Lightning does offer a 496 silent choice style system. Although due to the extended length of the runners, a shorter diverter is required. That is why Lightning's silent choice system comes complete with its own unique style diverter which is shorter than your factory system.

Ultimately Dana makes a great manifold style system but if you are looking for MAXIMUM power gains a tubular style header is the way to go.

Lightning says about a 40 hp gain on the 496 and 50-60 hp gain on the 496HO. Unfortunately I do not have any dyno sheets to share with you guys at this time.