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Old 02-06-2006, 06:22 PM   #1
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1983 31' International
Jasper , Georgia
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New Exhaust System?

As a new Airstream motorhomer, I am considering altering my engine in preparation for a major trip across country this coming summer. I am considering headers and upgrading my exhaust and maybe a new intake. I would like to hear from anyone who has added these improvements to a Chevy 454 engine. My goals are: improvement in power, better gas mileage (current is 6.5 - 7), and reduction in engine heat. Any help would be appreciated.
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Old 02-06-2006, 06:36 PM   #2
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1993 21' Sovereign
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You can go with a medium-rise intake manifold, coated headers to help reduce heat, and a free-flowing muffler system. If money is no object, you can also invest in a gear vendor's under/overdrive system.
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Old 02-08-2006, 07:33 AM   #3
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1984 28' Funeral Coach
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Geo, welcome to the forums! My 454 has had perhaps what you may want to follow. I replaced the oem leaky exhaust manifolds with Headman Coated Headers. Very inexpensive power / economy fix. Mine came from Summit Racing but some here prefer Jegs. Behind the reducers via 2.5 inch pipes are Flowmaster 70's and then 2.5 inch out in front of the rear axle via twin bowtie tips...cute!
I have posted a thread "more intake air" that you may want to have a look at. This air intake breather box is easy to fabricate and relocates the filter as well as increases airflow.
You may want to put a riser under your carb rather than go to all the expense of a new intake manifold. Half and inch to an inch makes a difference in cooling fuel and helping to avoid vapor locks.
My coach is a little different in layout to yours regarding the lack of cabinets and such but depending on your rear end ratio you will see some economy gains with the above retrofits. The gains in performance will be quite noticeable.
Avoid going bigger than 2.5 inch exhaust as you will suffer a loss of back presure and low end torque.
If you're planning lots of mileage a Gearvendor over/under drive unit may be in your future. Search "Gearvendor" for lots of posts here.
Let us know of your progress as you go forward.
BTW I'm turning close to 10 MPG with my coach. Last check was 9.44 MPG with 50 miles of city driving and generator running all day.
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Old 02-08-2006, 08:34 AM   #4
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1986 34.5' Airstream 345
Louisville , Kentucky
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I did a similar exhaust system using Hedmann headers and also 2.5" pipes all the way back. I also added an "H-Pipe" crossover just aft of the tranny shaft. Got everything from Jegs. I've chased a lot of gremlins out of mine (carb rebuild, new ignition, high-heat 9mm wireset, etc) but I get around 9 mpg when not towing my car and 8 when towing. I also seem to pull the hills a little better but that might just be my imagination.

Engine temps stay around 180 - 195 almost all of the time unles I'm pulling a long hard hill. Don't know about under the doghouse temps but after replacing my stock manifolds with the AIR system I'm convinced that things are cooler under there with not obstructions, lower turbulence and no 90 degree bends.

I run the stock cast iron intake.
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Old 02-08-2006, 12:11 PM   #5
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1991 35' Airstream 350
Windsor , North Carolina
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Gearvendor

Sorry, I don't find much in a search on gearvendor in this forum. Is there a website??
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Old 02-08-2006, 05:30 PM   #6
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Gear vendors

go to "Airstream motorhome forums" click on drop down "srearch"
type in "Gear vendors"
lotsa hits there.
yes they do have a website, Google search "Gear vendors"

Very nice unit but pricy, it is pretty much accepted they are the best unit out there.

ol'George
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Old 02-09-2006, 07:31 AM   #7
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Here's a link to the Gearvendors site..

http://www.gearvendors.com/
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Old 02-09-2006, 11:58 PM   #8
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Thanks!!

Thanks all,

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