496 Exhaust Manifold Replacements

[04-24Stealth]

Got water in all 4 port side cylinders over the weekend at Havasu. When I got the boat from Florida two years ago I was told I was in borrowed time with that manifold.

Looking at parts to replacement now. Are there any write ups on replacing the manifolds and possibly the risers.

Leaning towards going with stock replacements. Is there a better option? The boat rarely sees saltwater anymore but will be in the ocean at some point and flushed after.




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[Runs2rch]

Marine Industries West. Might as well add a little power while you are at it.

496 Flow Torque Exhaust Kit - Marine Industries West

DMP's new 496 exhaust kit is 17.5 tall and has been assembled using our proven Vortex exhaust technology. DMP's Vortex designs use exhaust scavenging technology to create maximum HP and torque. DMP is the first exhaust company to provide printed dyno results, and we stand behind our claims...

www.marineindustrieswest.com

 

[74 spectra20 v-drive]

I just bit the bullet on a set of Dana Headers from Marine Industries, was totally impressed with the guys out there and the product. I had to change props as i was breaking the one i had been using loose, big torque change for me for sure, plus they sound pretty nasty too.

 

[LargeOrangeFont]

These manifolds have to be a ton lighter too I’d imagine?

 

[02HoWaRd26]

I also have to say call MIW, i did on my 496, way lighter, better looking, better sound as well the power increase.

 

[HubbaHubbaLife]

Not to highjack but a quick question for those mechanically gifted on the thread..... I run a 496HO in ocean only. Always flush with Salt A Way and am curious how this induction system is designed to cool engine? I see where the water gets pulled in at the keel and I see where the water exits through my exhaust.... but where does the water actually travel through to cool engine? I'm told my manifolds will need replacing over time even though I flush religiously. Thanks.

 

[04-24Stealth]

Not to highjack but a quick question for those mechanically gifted on the thread..... I run a 496HO in ocean only. Always flush with Salt A Way and am curious how this induction system is designed to cool engine? I see where the water gets pulled in at the keel and I see where the water exits through my exhaust.... but where does the water actually travel through to cool engine? I'm told my manifolds will need replacing over time even though I flush religiously. Thanks.

From what I have learned reading about replacement there are a few head exchangers in the raw water system. Couple on the port side look like oil coolers then one big one in the middle up front that mixes with the coolants for the closed loop cooling system.


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[04-24Stealth]

I also have to say call MIW, i did on my 496, way lighter, better looking, better sound as well the power increase.
View attachment 910942 View attachment 910943 View attachment 910944

Those look amazing. I will have to give them a call. Just looking online looks like things will add up quick though but damn they look so good.


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[74 spectra20 v-drive]

They are pricey but... all stainless, they build the tail pipes custom to your boat and they are dual wall water cooled. Bob is the guy to talk to tell him that you saw some of his work on Cliff's Spectra and he will probably charge you more

 

[02HoWaRd26]

Those look amazing. I will have to give them a call. Just looking online looks like things will add up quick though but damn they look so good.


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Not to give away any trade secrets, but go there with a pocket full and talk to him. Mine obviously has more than just the headers i had E-Ticket do the stainless tails and then some other little Knick knacks to make it less ugly.

 

[04-24Stealth]

Thanks for the input guys. Next question, does anyone know if the red hose has a specific part number or will a hose of same diameter work?

This hose connect my stern drive pick up to the air valve.

Figured it’s a good idea to replace it now since it’s original 2004 or at least 2009 but I can’t find a part number for it.

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[Runs2rch]

These manifolds have to be a ton lighter too I’d imagine?

Up until 04, 496's were aluminum. Then they switched back to cast iron.

 

[Shrub Lurker]

Thanks for the input guys. Next question, does anyone know if the red hose has a specific part number or will a hose of same diameter work?

This hose connect my stern drive pick up to the air valve. View attachment 912163
Figured it’s a good idea to replace it now since it’s original 2004 or at least 2009 but I can’t find a part number for it. View attachment 912164


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bulk one and a quarter inch hose. Be careful the out drive oil tank hose is right under where that intake hose connects to the transom.

 

[SS-C]

What are these welds?

I have the same headers, but my risers are smooth and clean in that area.

The ones I have are either all one piece cast stainless steel, or they took the extra time to grind and polish out the welds.

I wonder why yours are like that?

Could it be their skipping a step in the casting / machining / polishing process, maybe they slipped past quality control, or simply trying to save money and that’s just how their sending them out now?

Whatever the reason, it definitely shows a difference.

I really like mine; they sound great and helped a bit with performance too!

 

[SS-C]

I just bit the bullet on a set of Dana Headers from Marine Industries, was totally impressed with the guys out there and the product. I had to change props as i was breaking the one i had been using loose, big torque change for me for sure, plus they sound pretty nasty too.

View attachment 910535 View attachment 910538 View attachment 910541

I also have to say call MIW, i did on my 496, way lighter, better looking, better sound as well the power increase.
View attachment 910942 View attachment 910943 View attachment 910944

Just a heads up in case you experience an exhaust leak with the Dana headers.
I did not have good luck with the blue Garlock gaskets they come with for the cylinder head to exhaust header/manifold connection. The gaskets burned through after the second outing. I replaced them, added new stainless lock washers with the bolts and torqued them evenly. Well, it happened a second time. I decided to go with the stock exhaust manifold gaskets and they have been good ever since, no more issues, no more leaks.
The blue gaskets between the header/manifold and riser work just fine.

 

[74 spectra20 v-drive]

Thanks for the heads up on the header gasket ill keep an eye on them. I tried to use remflex gaskets, I use them on my flat and had them on this boat with the Nicson headers but they were too thick, it baffled me but i had my son helping me and even strapped the header to my hoist and hung it so I wasn't trying to hold the dam thing up. the dana header was hitting a head bolt and would not bolt up... I love the remflex gaskets, made with graphite and have a 50% crush when installed. No idea on that weld, I the Dana is no longer on them either, maybe a change in the fixture? sure looks nice smooth