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Best 496 headers?

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Old 02-26-2007, 11:36 AM
  #31
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The dana product has a much larger manifold and a shorter riser tube. Overall height is still the same, but the stock merc part is short manifold and tall riser. The only issue is with stock PCM bracket. The dana product was developed on a late model 496. Mine is an 01' and will require longer legs on the computer bracket. Dana will machine and re-powdercoat your early model bracket to fit the new tubes and keep the computer in stock location w/o any other issues. If in doubt pull off your cowling, take a pic of port side, and send it to dana to verify.
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Old 02-26-2007, 11:45 AM
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I am not trying to stir the pot, just trying to learn.

This is the information I was talking about when refering to Raylar.

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Originally Posted by Raylar View Post
I thought I might chime in here to kind of even out the questions of horsepower and torque gains from exhaust upgrades on 496's. First, keep in mind that for any motor to gain horsepower or torque it must basically get more efficient. Obviously any things changed on a motor that increase the volumetric efficiency can increase power. There are basically three types of marine exhaust manifolds,

1. The tradtional old mercruiser log manofolds that came on the 350 thru 502 carburated and MPI motors from 60's thru mid 90's. these manifolds because of their log (all exhaust ports dump close to the head into a long square chamber and then exit a back end up thru a small vertical riser entrance) are very innefficient, heavy (iron) and were poor at letting the motor develop hp and torque.

2. The aftermarket and new Mercury (Gil) short runner, center riser manifolds. These are aluminum units like Eddie,, Revolution Imco, Gil, CMI E-tops and 496 Merc., etc. they all have similar short runners 8" - 10" that merge into center riser openings and definitly flow better than the old log type most boaters have been use to. They will definitly make more power and torque than the old log manifolds.

3. The tubular stainless and special cast units with long 18" to 24" semi-equal length with good merge collectors, like CMI, IMCO Super Powerflo, Stellings, Eichert Bassett, Dana, etc. will generally flow exhaust more efficiently than either of the two other types.

The real question here is the 496 engine. The stock 496 Merc (GIL) aluminum manifolds (type 2) are really pretty good units when compared to other (type 2) manifolds. Their individual runners and merge into the stainless steel round big radius risers with merge collectors can do a very good job of helping the 496 develop its great torque and good power. ESPECIALLY WHEN THEY ARE GIVEN EVER SO SLIGHT MODIFICATONS! If you were to take the turbulator plates alone out of the 496HO and dyno the motor you will see about a 15HP increase alone! So if you compare certain aftermarket manifolds (not type 3 tube headers) you will in most cases see no significant power increases from stock 496 manifolds.
If you are looking for more Bling, polish or paint the Mercury 496 manifolds, polish the stainless risers and you have some good look'in aluminum manifolds that work well and you will save yourself about $1500 minimum.
If your 496 is stock and you choose to step up to a good (type 3) header system you will probably see about 25-40HP net increase over the stock exhaust manifolds and risers with the "turbulators" removed, depending on your boats riser to transom configuration and muffler use if applicable.

Trust me when I say that Raylar has probably made more dyno pulls on stock and modified 496's with many combinations of exhaust than probably anybody in the industry short of GM and I have the dyno sheets to prove it! We have made over 525HP on a normally aspirated 496 with stock Mercury 496 exhaust manifolds (turbulators removed and manifold riser openings lightly ported.) This is about the limit, normally aspirated, for these stock manifolds.

If your plans are to go above 525HP with a 496 either normally aspirated or supercharged 496, then invest in a good set of (type 3) real headers or manifolds, you won't get there without them.
I am not trying to endorse or critisize any aftermarket exhaust manufacturers here, I am just trying to get the real world results of their use on stock 496's where I have my expertise.
Remember engines increase power from increased breathing and efficent use of fuel. The 496's need to breathe better on the intake side to make more power above 450HP and this will only come from improvements in heads, cams and intake manifolds, supercharger or turbo charger addtions . You are not going to get a 475HP from a stock 496 from just installing any set of headers and especially not from a set of $2000 manifolds. If you do, let me know how you did it.

Just some real world facts!

Best Regards,

Ray @ Raylar
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Old 02-26-2007, 12:09 PM
  #33
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Quote:
3. The tubular stainless and special cast units with long 18" to 24" semi-equal length with good merge collectors, like CMI, IMCO Super Powerflo, Stellings, Eichert Bassett, Dana, etc. will generally flow exhaust more efficiently than either of the two other types.
Quote:
If your plans are to go above 525HP with a 496 either normally aspirated or supercharged 496, then invest in a good set of (type 3) real headers or manifolds, you won't get there without them.
No problem Bill 3,

+ If you ask Ray currently, Im fairly sure he would still agree On the Dana's being one of the best, if not the best manifolds out there currently on the market I do also agree with Ray, if you want in to the 500hp or over range you either need cam & hd work or an Sc with the proper install.. These manifolds just help to bring you as close as possible without getting into that stuff..


Quote:
The dana product has a much larger manifold and a shorter riser tube. Overall height is still the same, but the stock merc part is short manifold and tall riser. The only issue is with stock PCM bracket. The dana product was developed on a late model 496. Mine is an 01' and will require longer legs on the computer bracket. Dana will machine and re-powdercoat your early model bracket to fit the new tubes and keep the computer in stock location w/o any other issues. If in doubt pull off your cowling, take a pic of port side, and send it to dana to verify.
tblrklakemo,

You are correct.. Also the manifolds are about 1.25" wider on each manifold compared to the OEM manifolds, so some twin applications may not be able to run them. You need to be at least 34.5" centers with no other obstructions to run them & thats if you shave the inside manifolds.. If you dont want to shave them then 35" or wider between centerlines with no obstructions is what you need.. I say that because some hulls have a single hatch lift inbetween the engines. So if this is the case you need to make sure you have about 1.25 to 1.5 inches in between the hatch actuator & the stock manifold for it to fit without shaving the inside manifolds.. FYI: They can only shave off between 1/8" to 1/4" total from each manifold..

BTW, if any of you guys need pricing or more info feel free to call me. We are distributors & Installers for Dana marine products..

Jamie / Lakeside Restorations 570-639-2628


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Old 02-26-2007, 12:09 PM
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Just increasing fuel pressure for full throttle is going to put the engine too rich at every other operating point. That's a rather crude way of tuning.

Also be careful of these horsepower claims. You can easily show huge horsepower gains, by putting on a new,shiny set of valve covers, and "correcting" to a more favorable set of standard pressure and temperature conditions for the dyno run. That's a very common cheat.

Michael
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Old 02-26-2007, 12:15 PM
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To add a few words to the subject,
We have dyno sheets available for any inquiring party. I don't know of any other exhaust manufacturer willing to provide that information for the 496 exhaust kit.

Re-programming is not needed. From what I understand, even on the Raylar engine upgrade, the only thing that gets changed in the ECM is the rev limiter. Can you benefit from additional ECM changes? Maybe, but we did not test for that in our dyno testing. The ECM modules were left completely stock.

Only late model 496HO engines require the fuel pressure increase. These engines do have a lean condition after an exhaust upgrade. Any other exhaust manufacturer who does not suggest the fuel pressure increase has obviously not done proper testing.

The lean condition was very obvious to us, we found it on the dyno, and in our water testing with a portable exhaust sensor kit. The fuel pressure increase brought the exhaust temperature back into a safe range.

DMP exhaust systems have several internal features that are not seen in most aftermarket exhaust systems. Our internal features were created to make real HP and Torque.
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Old 02-26-2007, 12:17 PM
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Quote:
Originally Posted by Michael1 View Post
Just increasing fuel pressure for full throttle is going to put the engine too rich at every other operating point. That's a rather crude way of tuning.

Also be careful of these horsepower claims. You can easily show huge horsepower gains, by putting on a new,shiny set of valve covers, and "correcting" to a more favorable set of standard pressure and temperature conditions for the dyno run. That's a very common cheat.

Michael

An average of a 3# fuel psi upgrade is not a huge like running a large increase for an SC application.. This is more of a tweek.. Jamie / Lakeside
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Old 02-26-2007, 12:23 PM
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Question. I looked on Dana's website and found the manifold. If I understand it right the 496 kit ($2550) comes with all needed. But it comes with "tube style" risers and to get the hp gains we would like wouldn't we need to get the "vortex *" risers which are $1060. Not sure about an exchange of the "tube style" for the "vortex *" riser $. Regardless we are getting real close to header money if not over and they have more bling factor to go with the hp.

Don't be offended by my (our) skepticism. There are a lot of exhaust systems for sale. If you can go ahead and post the dyno numbers. I am sure several of us would like to see them.

PM or email me with pricing. I am currently having my hull blueprinted, and depending on how that goes ($), I may be interested in more "go fast" stuff.

Thanks,
Bill
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Old 02-26-2007, 12:30 PM
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Quote:
Originally Posted by Bill 3 View Post
Question. I looked on Dana's website and found the manifold. If I understand it right the 496 kit ($2550) comes with all needed. But it comes with "tube style" risers and to get the hp gains we would like wouldn't we need to get the "vortex *" risers which are $1060. Not sure about an exchange of the "tube style" for the "vortex *" riser $. Regardless we are getting real close to header money if not over and they have more bling factor to go with the hp.

Don't be offended by my (our) skepticism. There are a lot of exhaust systems for sale. If you can go ahead and post the dyno numbers. I am sure several of us would like to see them.

PM or email me with pricing. I am currently having my hull blueprinted, and depending on how that goes ($), I may be interested in more "go fast" stuff.

Thanks,
Bill

The kits for the 496 applications include the vortex risers, they are not an additional expense. The NON 496 kits do not come with those risers, it is more of an Ala carte type of purchase.. The only thing additional to the cost is if you want them color powdercoated or hard anodized, and the fuel pressure regulator for the late 496 mag Ho's..

Jamie / lakeside

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Old 02-26-2007, 01:07 PM
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Another Question about Dana Manifolds. I currently have corsa silent choice. Do these risers mate to them, or to I need to get rid of them?
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Old 02-26-2007, 01:21 PM
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Quote:
Originally Posted by Michael1 View Post
Just increasing fuel pressure for full throttle is going to put the engine too rich at every other operating point. That's a rather crude way of tuning.

Also be careful of these horsepower claims. You can easily show huge horsepower gains, by putting on a new,shiny set of valve covers, and "correcting" to a more favorable set of standard pressure and temperature conditions for the dyno run. That's a very common cheat.

Michael
Just to clarify, the lean condition is not on the top end. The late model 496HO's have a lean condition from 3000 rpm to 3900 rpm. Although the air temperature readings were a little lower at wide open throttle, they were still slightly higher than desired. The 2-3 pounds of fuel pressure is a small change, but this fuel injection system is very sensitive. It fixes the lean condition and does not affect other points of running. Even after our fuel pressure change, it still does not blacken the transom. So idle is not a problem.
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