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Old 11-05-2021, 08:58 PM   #1
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Better mileage

looking at a 1991 Damon Challenger with a 454 in it, the appealing points are it only has 26000 miles, setting on new tires and is super clean inside and out, the problem is the owner says it only gets 4 to 5 mpg. I know that it should be better how much better I'm not sure, so what are some things that could be done mechanically to make it more efficient or is that a pipe dream
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Old 11-05-2021, 09:20 PM   #2
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Short answer is no... that about average..
Next answer is yes..
One slow down.. carry less weight..
Or how mechanical are you...?? or how big is your pocket book?
I have heard from a friend.. that he knew someone that pull 454 and put in diesel and got 15mph..
What I like about Chevy 454.. is there are so many mods out there.. but most cost more if you have to pay labor $$$$ then return in fuel savings... if you don't pay labor.. diy.. then pays off..
The real problem is the way they are geared... the diff gear has to be geared to get smogged down 454 over mountains..
That is way you are finally seeing 6 speed transmission in rv.. in some cases even more..
Are you mechanical ?
If you worry about fuel... then get a smaller home..
Good luck and let us know what you did and maybe better members then me will help you
2000 southwind storm, workhorse custom chassis with 7.4l vortec
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Old 11-05-2021, 09:25 PM   #3
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As above. And how much do you plan to drive. The more you drive, the more you're likely to pay off (or at least get closer) the upgrade cost.

Easy ones (slower speed, less weight especially if there are hills/mountains where you drive).

3 speed transmission doesn't help.

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Old 11-06-2021, 06:36 AM   #4
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How big is a Damon Challenger? I expected to get 6-7 mpg with my 454 and I usually get 9 mpg. I'm around 11,000gvw
1986 Itasca Sunflyer 22 ft P32 chassis with 454 engine
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Old 11-06-2021, 07:02 AM   #5
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You should be getting a little better than 4 mpg especially if you keep the speed below 65 mph. If you only have a 3 speed tranny , then you probably wont't get much better. You can add a few degrees advance to the timing and that will make quite a difference , but you will have to monitor the knock counts with a laptop and tuner pro software. Otherwise too much advance will destroy your engine.
Banks headers and cold air intake will make a difference as well.
1993 Tiffin Allegro Bay 32'
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Old 11-06-2021, 07:22 AM   #6
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I had a small class a with a 496 and it usually returned about 8mpg, i did get 4 mpg on one trip pulling a trailer nearly as big as the motorhome with a headwind.
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Old 11-06-2021, 07:27 AM   #7
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That sounds pretty typical for that era 454 cid engine. But it all depends on your speed, terrain and it you are towing a car. You might get 6 or so mpg if you slowed down to about 60 mph.

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Old 11-06-2021, 07:35 AM   #8
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I had a 32' class A with a 454 and it averaged between 6 and 7 mpg. Though on trips where I was doing a lot of stop and go driving in towns it could easily get down to 4 or 5 mpg. So what he's telling you isn't unreasonable, but you'd need to know where and how he's driving. If his foot is on the floor every time he accelerates then that's going to hurt the mileage.
You should be able to get right at 7 mpg doing between 60 and 65 on the interstate. Any faster and there is a notable drop in mpg. Get on secondary roads where you can safely run 55 or 60 and the mileage goes up - at least until you hit a town with a bunch of stop lights/signs.
As for suggestions on what to do, you could try a basic tune up. It made a difference on mine just changing plugs and plug wires. Also make sure the tires are properly inflated, underinflated will cost you in mpg.
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Old 11-06-2021, 07:56 AM   #9
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Originally Posted by GLT3 View Post
looking at a 1991 Damon Challenger with a 454 in it, the appealing points are it only has 26000 miles, setting on new tires and is super clean inside and out, the problem is the owner says it only gets 4 to 5 mpg. I know that it should be better how much better I'm not sure, so what are some things that could be done mechanically to make it more efficient or is that a pipe dream
Unless you are planning to keep this RV for many, many years, my guess is it wouldn’t be wise to spend thousands on an upgrade. In reality, you will never recoup your investment when you decide to unload it on the next owner.

I don’t know what size fuel tank the Damon has, but if it’s relatively small, I believe having to refuel often would be a burden. One thing to consider would be a second tank, professionally done with safety procedures addressed, to allow more distance between having to refill. Tweaking and tuning the 454 would be wise and there are minor things that could modestly help.

I also believe that increasing your mileage by 2 or 3 mpg will only save you around $600 a year if you drive 4000 miles, so it would take you a good while to recoup a large investment to modify.
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Old 11-06-2021, 08:03 AM   #10
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I think you are getting "Apples and Oranges" responses here.

Before you take any action you need to know what you have. A 1991 Class A with a 454 GM engine is right on the cusp between the carbureted version with the TH475 3 speed transmission and the TBI with the 4L80E 4 speed transmission. The carbureted version is the Apples...the TBI version is the Oranges.

The answers about what to expect for fuel economy is different depending on the version chassis you have.

If it is the carburetor version with 3 speed transmission getting 5-6 MPG is normal if your speed is held at 60 MPH or below. Remember these were designed for 55 MPH speed limit! Driving it 65-70 will get you 4-5 MPG!

The TBI version with the 4 speed transmission should get 6-7 MPG if driven 60-65 MPG.

If you want to spend money to get better fuel economy the answers are different depending on the version that you have!

First, determine your chassis. Does it have a carburetor? Does the transmission have an overdrive? Once you know those things we can give you more specific information on modifications to meet your goals.
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Old 11-06-2021, 10:19 AM   #11
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When I had my old rig with a 454 (2.5 dual exhaust and Performer intake) I had a saying " this rig will go as fast as you want to pay" sums up mileage, fast pay more. Rig would cruise 80 MPH if you wanted to pay.
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Old 11-06-2021, 03:29 PM   #12
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Many years ago, after we sold our KOA campground, we bought a 1987 Georgie Boy Encounter (38 ft w/ a tag) and it had a carby 454, and a 3 speed TX, and got 6-7 MPG at 60 MPH @ 3200 RPM. A year into it, and I changed the rear end third member at a shop in Denver. The next 5 years she got 9-10 MPG @ 60 MPH @ 2600 RPM.
We put just over 125 K on that old girl, and I figured it was worth it.

Mike in Colorado
2004 Fleetwood Pace Arrow 37c, 8.1 gasser, (Jezebel) Ultra RV ECM / TCM, plugs wires, and rear track bar, PPE deep Tx pan, Bilstein's, Sailun's & Sumo's all round, pushed by a 2002 Grand Caravan, on a Master Tow Dolly.
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Old 11-06-2021, 05:10 PM   #13
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Just my opinion here, if I was buying a MH for shorter trips and weekend getaways to the lake with the occasional vacation thrown in I wouldn't be too worried about MPG, but if you plan to do a lot of long hauls, maybe some cross country trips, maybe you're retired, I would look for something more economical, maybe a diesel.
Brian, 2011 Winnebago Via Class A on Sprinter Chassis
Tucson, AZ
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Old 11-06-2021, 06:35 PM   #14
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The difference between 5 mpg and 7 mpg is about $1200 per year with todays prices if you drive 6,000 miles. Not a big deal in the overall cost of owning a motorhome. If it still has the stock exhaust and intake systems you might improve performance and economy with Banks system. However, depending on how many miles you will drive each year, it might take several years just to break even. What's your intended use?
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