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Old 12-15-2021, 02:16 PM   #1
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Engine swap - 454 to 12v cummins

Hello all - new here and learning... at least trying too.

I have a 84 Airstream motorhome in dire need of work. Outside of all the interior bits and bobs that need repair, the 454 is duff (not the beer... but kinda needed a few after realizing the PO lied about the engine). My bad... shoulda checked, oh well.

Anyway - I really want to put a diesel in there and have found a 12v with 102 miles on it. It has been removed from the vehicle so 'who knows'.

So - my question is (are) -

1. Any ways to check if the engine is decent? Get a mobile mechanic to look at it?

2. I was looking for a 'transmission' - any recommendations on transmission. Obviously I want to keep the revs low (reasonably low) and maintain ~65 mph to get the best mpg possible. Last communication with the guys said he has "47rh, turbo 400, at542 Allison'. I'll have to decipher that.

3. I know the 12v fits but the turbo needs to be move so I'll need a bunch of other parts, hoses, etc is there a decent place to get parts that's reliable and priced well?

4. Injector pumps?

In hindsight there are way to many questions here... is there a sticky thread for us novices ?

Any advise... or traps to avoid for newbies would be greatly appreciated
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Old 12-15-2021, 02:44 PM   #2
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There are a number of issues that you will be dealing with. fuel system hosing, (feed and return) rear end ratio, possible emissions testing, depending on state you are in, engine mounts, trans mounts, cooling system and the list goes on and on. Things you don't even think about like driveshaft length, exhaust system ( a diesel will plug up a muffler that is designed for a gas engine ). There are so many small things. Throttle linkage, does it have vacuum operated power brakes. Mounting the accessories, power steering pump, a/c compressor, alternator. The engine either needs to drop out the bottom or come out the front. Do you have the equipment to do that ?
I really don't mean to rain on your parade but you aren't talking an easy task here.
Best advice is find another 454 and spend your time and energy enjoying the RV instead of dumping the extra time & money into it that you will never recover from this long & complicated project.
If what you really want is a diesel then fix the Airstream, sell it and buy what you really want.
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Old 12-15-2021, 02:45 PM   #3
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Sell it for what you can get and lick your wounds. You are entering uncharted territory and you'll way out spend the pleasure you will get out of your "Frankenstein".
Why would anyone remove an engine with only 102 miles on it?
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Old 12-15-2021, 02:45 PM   #4
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Originally Posted by Roy-c View Post
There are a number of issues that you will be dealing with. fuel system hosing, (feed and return) rear end ratio, possible emissions testing, depending on state you are in, engine mounts, trans mounts, cooling system and the list goes on and on. Things you don't even think about like driveshaft length, exhaust system ( a diesel will plug up a muffler that is designed for a gas engine ). There are so many small things. Throttle linkage, does it have vacuum operated power brakes. Mounting the accessories, power steering pump, a/c compressor, alternator. The engine either needs to drop out the bottom or come out the front. Do you have the equipment to do that ?
I really don't mean to rain on your parade but you aren't talking an easy task here.
Best advice is find another 454 and spend your time and energy enjoying the RV instead of dumping the extra time & money into it that you will never recover from this long & complicated project.
If what you really want is a diesel then fix the Airstream, sell it and buy what you really want.

Good advice!
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Old 12-15-2021, 03:13 PM   #5
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This is actually a pretty common thing... especially in the Dodge Travco world where 440's get swapped for 6BT's all the time.
My best advice is to start with a more or less running and driving Cummings equipped pickup truck, etc of the 12 valve era. That way you can have access to all of the parts and accessories from both vehicles as well as a matched engine and tranny. I do know that the old 440 motor mounts in the Dodge M500 chassis motorhomes work well for the BT6. Not so sure about your GM chassis. You will probably need to notch the frame for turbo clearance. Cutting and welding will need to be done here and there along with other custom stuff but it's not rocket science
Also - don't overlook old Grumman delivery vans like they used for Frito-Lay delivery trucks, etc. They are usually BT4 equipped but sometimes you can find a gem. Isuzu trucks are another possibility. Bonus points if you go with a manual tranny or even include a 4X4 swap.
Sounds like a fun project! Good luck.
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Old 12-15-2021, 03:23 PM   #6
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The 454 weighs 500 or 600 lbs, the Cummins weighs twice that. When you find a trans to fit the Cummins that will add another couple hundred lbs over the old trans.
You can rebuild the 454 way cheaper then you can a cummins that may be junk.
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Old 12-15-2021, 08:05 PM   #7
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Thanks all - I appreciate the comments. 77Travco is on the money with these being used a lot with swaps, a reasonable number in Airstreams.

It really would be a chore.. big time, but the benefits outweigh the cons.. at least at the moment. The other side of the current 454 that bugs me is that is conks out after 10 minutes unless I keep the revs up.. I think it's an electrical issue, not sure tho'.

cheers -
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Old 12-16-2021, 06:27 AM   #8
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Quote:
Originally Posted by Petess View Post
Thanks all - I appreciate the comments. 77Travco is on the money with these being used a lot with swaps, a reasonable number in Airstreams.

It really would be a chore.. big time, but the benefits outweigh the cons.. at least at the moment. The other side of the current 454 that bugs me is that is conks out after 10 minutes unless I keep the revs up.. I think it's an electrical issue, not sure tho'.

cheers -
Pete
Many old coaches may not worth the effort but the antique and collectables like Travco, Airstream, Barth, Unger, etc certainly are. I had a buddy that swapped his Travco 270 over and he loved it. M500 chassis Dodges came with 4:56 gears and 34" tall tires on 19.5" wheels so it works well with lower RPM's.
My kid brother has done several of these swaps into pickups. He has a Cummins powered 1987 Chevy Dually 4X4 that is his daily driver.
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Old 12-16-2021, 06:55 AM   #9
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I know a guy here that swapped a Cummins into a MH like yours. I can't tell you the exact make and model. I know he worked on it a long time, anyway it sat partly done for a long time. If you're handy enough to do most of it yourself you are in good shape. If it is what you want go for it. There are easier ways to make the MH work but do want you want no matter what others say.
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Old 12-16-2021, 07:14 AM   #10
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It can be done but, the changes will also include the structure components such as motor/transmission mounts, shocks, etc...
Then wiring harness, fuel tanks, fuel lines, fuel filters, electronics, just a few items, but it can be done.
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Old 12-16-2021, 07:37 PM   #11
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If you're mechanical enough, it's relatively straightforward to do the swap.
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Old 12-17-2021, 12:53 PM   #12
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Finnegan swapped a 454 for a 12 valve Cummins in a Chevy 1 ton ramp truck.
Lots of work! He purchased a ex military tow truck with a Cummins and used lots of parts from one truck to another. Great videos.
The big challenge is getting the rear end ratio correct, the heater and A/C working, the instruments working, and a host of others.

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Old 12-17-2021, 03:45 PM   #13
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Quote:
Originally Posted by Petess View Post
Hello all - new here and learning... at least trying too.

I have a 84 Airstream motorhome in dire need of work. Outside of all the interior bits and bobs that need repair, the 454 is duff (not the beer... but kinda needed a few after realizing the PO lied about the engine). My bad... shoulda checked, oh well.

Anyway - I really want to put a diesel in there and have found a 12v with 102 miles on it. It has been removed from the vehicle so 'who knows'.

So - my question is (are) -

1. Any ways to check if the engine is decent? Get a mobile mechanic to look at it?

2. I was looking for a 'transmission' - any recommendations on transmission. Obviously I want to keep the revs low (reasonably low) and maintain ~65 mph to get the best mpg possible. Last communication with the guys said he has "47rh, turbo 400, at542 Allison'. I'll have to decipher that.

3. I know the 12v fits but the turbo needs to be move so I'll need a bunch of other parts, hoses, etc is there a decent place to get parts that's reliable and priced well?

4. Injector pumps?

In hindsight there are way to many questions here... is there a sticky thread for us novices ?

Any advise... or traps to avoid for newbies would be greatly appreciated

I had contemplated switching from the twin 454's 330hp in our boat to diesels . The reason for repowering is the engines have 1800 hrs. on them.

A good buddy has twin Cummins 250hp Turbo 4 cylinder diesels in his boat . He averages twice the fuel economy of our boat , at lower RPM and runs at the same speed .

However , I was having a hard time with resolving the " return on investment" . I could not spend the cost of the diesel repower on gas in the 10 yrs. of boating we have left.

What sealed the deal was when one of his engines experienced a fuel pump failure . The cost of the fuel pump , not including labor was $6K .

I am currently repowering our boat with 2 new 454 350hp engines for a total of $10K including engines and labor .

I just couldn't justify the cost switching to diesels in the boat and I would think the same way about changing our MH to diesel .

If someone thinks repowering from gas to diesel will save them money in the long run . I would like to see their method of estimating the cost.

From a cost perspective a new Fuel Injected 454 would be more cost effective .

Just my opinion , everyone is certainly entitled to make their own decision.
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Old 12-17-2021, 03:48 PM   #14
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If you're mechanical enough, it's relatively straightforward to do the swap.
I wish I had a Crystal Ball.
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