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Old 11-11-2008, 03:46 PM   #15
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1989 34.5' Airstream 345
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Did you notice a big difference in your intake glen?? How did you fabricate the tops and bottoms of your intake?
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Old 11-11-2008, 04:37 PM   #16
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Not a big difference but it's there.

Used a top and bottom from Summitt, for a thinner filter.

Easy DIY job.
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Old 11-11-2008, 05:28 PM   #17
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Smile 1990 Airstream Classic 250 - carb.

I did the cold air intake, headman's headers, and a US Gear overdrive. Just completed a 5000 mile trip and averaged about 3 MPG improvement.

The overdrive dropped the RPM from 2800 @ 60 to 2200. Much quieter in the cabin.
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Old 11-11-2008, 07:17 PM   #18
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Pop Rivet, I'm curious of course... Are you saying that you did all of the improvements and only got 3mpg improvement or the cold air intake did it?

I'm hopeful of getting that much improvement out of the Gearvendor addition alone.

Also do you know your rear end ratio?

I had a discussion with Gevin at Falluminum and he's got an engine man in GA that may be my kind of guy to do the engine rebuild / tranny swap / gearvendor add on.

If we could keep gas under $2 I can afford to keep Airstream One on the road next year as my work vehicle...maybe.
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Old 11-12-2008, 05:07 PM   #19
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454 improvements

I don't really know which improvement contributed most to the 3 mpg increase in gas mileage. I suspect it was the headers. I also suspect the overdrive unit did not contribute much to the mileage. My unit is small (25 foot) and I was getting 10 mpg before the improvements, 13 mpg after. The 13 is hiway driving at around 60 miles per hour. That's better than my '89 454 pickup was getting. It got about 10 mpg all the time. I really don't know what the rear gear ratio is.
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Old 11-12-2008, 05:17 PM   #20
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Using a scan tool, I can say without question that even with a cold air intake, the temp of the air entering the engine is typically warmer than the outside ambient temp. Of course in winter, when it's cold out (say around 20 or maybe 30) I have seen intake temps around 80-90 b/c inevitably some engine heat does get drawn in.

Summer time, when it's 80 out, it is not uncommon to have 120+ intake temps.

I agree though, intake temp most likely is not the culprit though....
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Old 11-12-2008, 06:08 PM   #21
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Quote:
Originally Posted by Pop Rivet View Post
I don't really know which improvement contributed most to the 3 mpg increase in gas mileage. I suspect it was the headers. I also suspect the overdrive unit did not contribute much to the mileage. My unit is small (25 foot) and I was getting 10 mpg before the improvements, 13 mpg after. The 13 is hiway driving at around 60 miles per hour. That's better than my '89 454 pickup was getting. It got about 10 mpg all the time. I really don't know what the rear gear ratio is.
Can you run w/o o/d to ck mpg's.

I did quite a bit to our old 454 Burb, (no o/d) with just about the same results. Worked out well over 165k though.
The headers, made the most improvement in power while towing, I also averaged about 13 while towing.
I would guess the majority of your improvement was in that 600rpm decrease.
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Old 11-12-2008, 07:08 PM   #22
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Yup, I'm with Bob on this one.

The headers will provide more bottom end torque, better engine cooling, and better breathing or should that be exhaling?

I'd think that slowing the motor down via the OD is the main culprit in keeping more gas in the tank.

Now if you can figure out how to burn all the gas going into the motor and keep less of it from exiting on the exhaust end then you'd really have a better MPG number.

Colder air helps but it's all a sum total of the $'s spent.

FWIW I actually bought regular gas in GA today for $1.84 Oh YA!

At this price the Airstream can come back out and I can get out of these darn hotels!
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Old 11-14-2008, 06:10 PM   #23
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On the next trip, I'll just have to do a mpg test with and without the OD
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Old 11-16-2008, 04:44 PM   #24
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Pop Rivet, I'm going to be heading down to my house in Belleview after Thanksgiving. We might have to hook up and talk about all those improvements.
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Old 12-05-2008, 07:36 PM   #25
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Info on carb spacer: (phenolic resin recommended; 4-hole for velocity)

Spaced Out--How to Choose a Carburetor Spacer - SummitRacing.com

Mr. Gasket: #3404 spacer; #3712 Heat Shield; #9710 Pressure regulator (set to factory number);
http://go.mrgasket.com/pdf/carb_fuel_sys_acc.pdf

There may be changes necessary to the throttle linkage, but, if it is cable, just check for binding and re-mount (see catalog above; use JEGS or SUMMIT for parts. Replace the throttle return springs, you want positive action. (There are some slick, smooth teflon-lined throttle cables out there -- cut-to-length -- that can be adapted)

So, on cleaned manifold, mount paper gasket, mount heat shield, mount gasket, mount spacer, mount gasket. Install "dry" gaskets.

I recommend ARP studs, longer, to mount all this. You'll want to install and measure -- ballpark -- to get the right height. Mainly a matter of "tall enough, but short enough to not interfere with carb op.

ARP Carburetor Studs Carburetor Studs - Black Oxide - 5 - 16-18 - 24 in. x 3.200 in. Long - Kit | ARP | 200-2408
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Old 12-05-2008, 08:55 PM   #26
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1984 pace arrow motorhome fuel problems

I'd also replace ALL soft vacuum lines with new.
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Old 12-05-2008, 09:06 PM   #27
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Quote:
Originally Posted by REDNAX View Post
We experienced that exact same problem with our previous 27' Winnebago motorhome. The horrible condition of I-94 through Detroit cracked the old rotting rubber fuel line from the tank to the pipe along the side of the frame. As a temporary fix I ended up tapping into the generator feed line to get us on the road again.

There is a thread on dropping http://www.airforums.com/forums/f311...ure-25587.html the fuel tank for refurbishment. Worth reading.

Brad
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Old 12-06-2008, 10:09 AM   #28
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Exactly solving this air intake problem

While towing down thru South Texas one weekend I was listening to the San Antonio talk radio. The program was a typical type call in show for automotive problems and discussions. This question on intake air and engine performance came up and was very enlightening....especially for owners of all diesel powered vehicles.....the jest of it was production intakes are not doing the job. You need to "open up the intake and get a source "up front" away from the engine heat. The show host owns a very good business in San Antonio, Texas. If you call him he will tell you what you need to do..(no pressure or "selling"), or if your in the area...take it by and his shop can do the job. It is an easy fix and really beneficial. I did it on all my pickups.
I have no relationship with them....just like their work and ideas.
Cambridge Auto Center

9823 Fredericksburg Rd
San Antonio, TX 78240 Map
  • (210) 697-9600
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