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Old 11-09-2020, 06:45 PM   #1
Mini-Skoolie
 
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Join Date: Apr 2019
Location: Everywhere
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Year: 1994
Chassis: GMC
Engine: 454 Big Larry
454 engine swap

After 2 years of building, Ive slowly started to realize the 454 gas motor in my bus is on its way out. I should have known, based on the 15-40 motor oil recommendation someone put on the oil fill, that the motor was a bit worked. There is at least one collapsed lifter and it smokes quite a bit Sure, I could easily rebuild it. Probably for cheap. Crate motors are around $1,500. But the 454 gets around 6-8mpg and with the build out inside I feel like it could be more in the range of 5-7mpg.

My thought was if I could increase the mpg to 10-15 that i would save quite a lot of money on fuel. I am a drifter so I do travel quite a bit on my own, however as a photographer, sometimes my work involves traveling cross country. With the amount I drive, I figure I could save around $3,000 a year on fuel with an efficient diesel swap.

My question, what do people think is an ideal candidate for an engine swap? I have heard the 6.5l diesel is a good fit and could mate up to my trans which could make the process easier and cheaper. I feel confident I can do all the work myself. But would like help with brainstorming power plant options.

My budget would be the cost of rebuilding the 454 and around 4 years of fuel savings, which would be in the range of $12,000-14,000.

Thanks you for any insight you can share!!

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Old 11-09-2020, 07:00 PM   #2
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the 6.5 wont give you 10-15.. im not even sure they got that in a pickup truck..



to go diesel not only do you need to think about an engine that fits.. you have the supporting cast too..



what trans is in it? if the bus is a 94 id expect to see a 4L60E which means you need to control that electronic transmission separately sicne the engine computer will be gone.. can your transmission handle the high torque of a diesel engine?



that 454 likely had a top RPM of 4000-4500 so you'll need to examine rear gears .. a diesel typically redlines at 2500-2800 RPM and wont give you 10-15 MPG running there.. it would want to cruise noticeably lower RPM..


a diesel engine is going to be double or triple the weight of that 454.. depending on which engine you use.. can your front axle / suspension / hubs / springs handle it?


other supporting cast you'll need to think about is accesory drives (does the vus have power steering, A/C, etc?


what type of brakes? are there any vacuum operated accessories that wont operate with a diesel (no vacuum)


dashboard gauges - the engine ECM will be gone.. are your gauges tied to the computer or separate?


physical room for your engine of choice?


all thigs to think about which can add cost and effort to the swap.
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Old 11-09-2020, 07:39 PM   #3
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Swap in a 350 with a turbo if you want better mpg, actually let me edit and say a 383 might be better with the longer stroke more torque at lower rpm. and still a turbo.
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Old 11-09-2020, 08:08 PM   #4
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Later 6.2s and 6.5s had TPS in the injector pump for controlling the 4L60E / 4L80E, but the torque converters are typically different from gas to diesel as well. Not to mention the diesel trans will have beefier internals. Not sure a standard 4L60E or even a gasoline version of the 4L80E can handle the torque of the diesel options.

If I were to swap a 454 for diesel, I would likely go with an older 3.9 Isuzu from an NPR truck. I think on a 94 the gauge sensors do pass through the PCM for use in determining fuel and shift points though.
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Old 11-10-2020, 02:20 PM   #5
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Your 94 454 is at the end of a long line of smog engines, it's specs are horrible, if you were to rebuild it, you could change the cam and stuff to optimise it for the RPM range you are running and get more power and economy, or you could find a newer GMC based vehicle with the 8.1 engine and swap that drive train into your bus
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Old 05-14-2021, 07:38 AM   #6
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Hey! After quite a few months of work over the winter, I’ve saved up some money and I am going forward with a 6.2 L92 LS engine swap. Behind it I have a 6l80 transmission. I have a Truck//RV cam ordered as well as headers, upgraded internals and planning some head/intake work as well. I’ll post some stuff on here- but will have videos and other posts on my Instagram @squallythetrolley and @smellybagofdirt . Thank you for the feedback and information from last year! The dream is coming to life! The first video of the swap can be found below -
https://www.instagram.com/p/CO1Nyrzj...=162njknmeydh1
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Old 05-14-2021, 08:48 AM   #7
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Ohh man!! You're throwing an LS in there?! That's going to be a screaming trolley! Haha. Can't wait to see this thing driving!
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Old 05-14-2021, 09:56 AM   #8
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Hah. Me too! Before it sat for 2 years it would run cruise control at 65 no problem... on the flats. Hill, however ..... it did not like. Even the small ones would make it struggle to go 30mph . The bus weighs around 12,000lbs so with the LS properly tuned I’m hoping it’ll scoot around! Yeehaw ��
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Old 05-14-2021, 10:17 AM   #9
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Are you going to go all out and have it supercharged, turbo, cam, etc? Either way, the LS is an amazing platform with lots of customization options. You'll be able to make it drive EXACTLY the way you want it to!
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Old 05-14-2021, 10:37 AM   #10
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I am doing the conversion to be able to drive over mountain passes without the hazards on and to get better gas mileage than that 454 gave me.... hoping for around 50% increase . From 5-6 up to about 9mpg. With that, I’m doing a truck/RV cam as well as a rebuild and some extra shiny things on the inside - headers and some head / intake machine work. No supercharger for now lol
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Old 05-14-2021, 11:02 AM   #11
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A rebuild or replacement of your 454 will be your least expensive option, if you have not already bought the LS.
It will also likely improve your fuel mileage with a fresh engine.

Is the current engine carbureted or fuel injected?
A fuel injection conversion, (after engine rebuild), is another good way to improve MPG if it is a carb model.

Good luck, going forward...
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Old 05-14-2021, 11:27 AM   #12
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An LS swap in a trolley, I like it
Don't know if it will help achieve the fuel mileage you're looking for, but definitely a nice project.
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Old 05-14-2021, 02:01 PM   #13
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Engine: 454 Big Larry
Similarly shaped 3500 rigs with the 6.0 and 6.2 are getting upwards of 10 , so I don’t see why 9-10mpg is an unrealistic number for the swap. By the time I do an EFI conversion on the 454 and rebuilt it, I’d be looking at around 3,000 . The difference in price for the LS swap will be made up in fuel costs over the following years, as well as endless smiles driving that thing across the country.
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Old 05-14-2021, 02:17 PM   #14
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Quote:
Originally Posted by Squally the Trolley View Post
Similarly shaped 3500 rigs with the 6.0 and 6.2 are getting upwards of 10 , so I dont see why 9-10mpg is an unrealistic number for the swap. By the time I do an EFI conversion on the 454 and rebuilt it, Id be looking at around 3,000 . The difference in price for the LS swap will be made up in fuel costs over the following years, as well as endless smiles driving that thing across the country.
I sure like your attitude, countless smiles!!
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Old 06-24-2021, 08:01 PM   #15
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Thats what im talkn about. Nice choice!

Isnt the 6.0 in G3500 short buses same as a LS 6.0 block? Just different heads/cam/intake?

An old 454 is that bad on a hill eh?
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Old 02-16-2022, 10:30 AM   #16
Mini-Skoolie
 
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Join Date: Apr 2019
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Year: 1994
Chassis: GMC
Engine: 454 Big Larry
Update: it’s been 6 months and like all things bus building…. the process has been slooowwww and way more expensive. I currently have the engine dropped off to get some machine work done! Having the cylinders bored, some porting on the heads and a custom camshaft ground up for its new life in the trolley.

Here is a picture of the inside and what will hopefully be scooting down the road by this LS engine!
https://www.instagram.com/p/CWtP_eQJ...dium=copy_link
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Old 02-16-2022, 03:50 PM   #17
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Yes I did the engine, trans, rearend swap and it is a mountain of work, I believe your LS swap will work out the best, beautiful interior, what an imagination and creativity.
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