Running a custom made dry stainless header on 4.3 i/o?

lblevins

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Feb 25, 2014
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Im setting up a boat I just got and would like to know if its possible to go from wet mani and risers to dry stainless custom built headers like you'd build for a car? I have built alot of headers but am new to boats I know the theory of the wet is cooler but is that its only function I can run a little water injection port into each runner to cool it if I need to. I just dont see why I couldn't if anyone has any light to shed please lmk. Thanks and godbless
 

achris

More fish than mountain goat
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May 19, 2004
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27,468
Re: Running a custom made dry stainless header on 4.3 i/o?

Even with your little water injection port the heat produced would be too high for SAFE use inside a standard engine bay. Have a look at the design of boat with dry stacks and you'll see how much difference there really is with a wet system. You also have noise and vibration/resonance issues to deal with on a dry stack that just don't happen on a wet system.

Many have looked into to it, and almost all stay with the wet system.

Chris.....
 

agallant80

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Oct 25, 2010
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2,328
Re: Running a custom made dry stainless header on 4.3 i/o?

There is no airflow over the manifolds of marine engines therefore they must be water cooled. Also the engine is in an enclosed compartment. Fuel fumes can ignite because there is no place for them to go, hot manifolds will ignite fuel fumes. Using auto headers on a boat will result in a fire or explosion sooner or later.

Its tempting to look at your motor and see a GM block but that is about all it has in common with a car. Even the starter and alternator are marine rated as to not cause a spark that can ignite any fuel vapors that are in the bilge.
 
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lblevins

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Feb 25, 2014
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Re: Running a custom made dry stainless header on 4.3 i/o?

ok well this all is understandable and I appreciate your input to my ignorance. This is all new to me but im very excited and hopeful. I was reading about people changing there mani's and risers ever few years and thought it'd be better to just get rid of and save the money while doing something custom but what you all are saying makes since.

In response though I was considering making a fiberglass bonnet with slotted air inlet and exit for air in and out with electric fans to keep the bilge much cooler. Also had planned on wrapping the headers in heat wrap to keep the temps down and then a 1 way check valve into each runner with a small nozzle to inject enough water too cool down the pipes. I really like doing custom fab work and think it would be very unique. I really appreciate the input guys, also was looking at going with a thru hull setup with this idea.... I know some frown on this but the lakes im close to here in oklahoma most people run thru hull or bbc v8s in the speed boats so im use to hearing the roars and so are most.
 

Bondo

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Apr 17, 2002
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71,088
Re: Running a custom made dry stainless header on 4.3 i/o?

ok well this all is understandable and I appreciate your input to my ignorance. This is all new to me but im very excited and hopeful. I was reading about people changing there mani's and risers ever few years and thought it'd be better to just get rid of and save the money while doing something custom but what you all are saying makes since.

In response though I was considering making a fiberglass bonnet with slotted air inlet and exit for air in and out with electric fans to keep the bilge much cooler. Also had planned on wrapping the headers in heat wrap to keep the temps down and then a 1 way check valve into each runner with a small nozzle to inject enough water too cool down the pipes. I really like doing custom fab work and think it would be very unique. I really appreciate the input guys, also was looking at going with a thru hull setup with this idea.... I know some frown on this but the lakes im close to here in oklahoma most people run thru hull or bbc v8s in the speed boats so im use to hearing the roars and so are most.

Ayuh,.... Welcome Aboard,.... That's on Saltwater run boats,....

Not much saltwater in Oklahoma,...

The Only way yer plan can work is with a Fully Open motor area,...
No amount of ventin' is gonna cut down on the Fire hazard,...
 

lblevins

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Feb 25, 2014
Messages
6
Re: Running a custom made dry stainless header on 4.3 i/o?

Well I guess it'll be mani's and risers.. lol.. I know you know your stuff bondo so I wont question you. Do you by chance know if a 96 vortec 4.3 will fit in my boat with the non vortec 90 4.3? I have to install an engine and found a 96 4.3 vortec with 60k miles out of a rolled blazer. I bought my boat with a cracked block so cheap I couldn't pass it up.
 

Bondo

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Re: Running a custom made dry stainless header on 4.3 i/o?

Well I guess it'll be mani's and risers.. lol.. I know you know your stuff bondo so I wont question you. Do you by chance know if a 96 vortec 4.3 will fit in my boat with the non vortec 90 4.3? I have to install an engine and found a 96 4.3 vortec with 60k miles out of a rolled blazer. I bought my boat with a cracked block so cheap I couldn't pass it up.

Ayuh,.... Should be a drop-in, plug, 'n play swap,....

After ya get the proper intake manifold,...

Michigan Motors sells the cast iron intake, that fits the Vortec head pattern,...
 

lblevins

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Feb 25, 2014
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Re: Running a custom made dry stainless header on 4.3 i/o?

Awesome, thank you so much! :)
 

Bondo

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Last edited:

thumpar

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Jun 21, 2007
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6,138
Re: Running a custom made dry stainless header on 4.3 i/o?

Change the core plugs to brass on the replacement engine.
 

captmello

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Jun 30, 2008
Messages
3,848
Re: Running a custom made dry stainless header on 4.3 i/o?

You may need to switch to an electric fuel pump as well. It needs to be wired properly though an oil pressure sensor.
 

Walt T

Lieutenant
Joined
Mar 16, 2002
Messages
1,369
Re: Running a custom made dry stainless header on 4.3 i/o?

All that work and expense, even with the dry headers wont get you the power increase you're looking for. A Vortec will help slightly but it's still just a 6 cylinder.
 

KD4UPL

Senior Chief Petty Officer
Joined
Feb 13, 2010
Messages
679
Re: Running a custom made dry stainless header on 4.3 i/o?

My boat is only used in fresh water. It's a '97 model. The manifolds and risers are original. You shouldn't have a problem.
 
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