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Old 06-20-2018, 07:55 PM   #1
jarrodblake
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I need some advice on which swap I should do. To get better MPG for the money. C30

So I am getting close on finishing my c30. Should be in paint next week. So I have a 1970 C30 ramp truck. It has the stock 4 bolt main 350 with 68,000 original miles. I assume the trucks weight is somewhere around 7-8k and I get about 4 MPG.

So in my quest for better gas mileage this is what I have come up with. Please correct me if I am wrong.

Option 1

My first thought was to install a Holley sniper EFI conversion kit and install a HX35 turbo I have. I can probably do the conversion for a little over 2k over time. I would do the EFI first then the turbo later. So $1,400 up front. then another $1,000-1,200 down the road when I turbo it. So a total of $2,400-2,600 However I don't see getting any more than 10-12 MPG out of it. That said I have a Chevy NV4500 getting ready to go in so that could help MPG. But the cost to do so are more than I want to spend for what I would get out of it. So I probably will not go this route


Option 2

Would be a 6.2 Diesel. I can get one for around $800 that is complete and running with low miles. I have access to two one with 82k that has been sitting for years and one with 125k that I know runs. They will bolt to my nv4500 and I can probably do the complete swap and turbo it for $1,400. Minus me selling the stock engine and junk 4 speed trans let's say $500-600. So around around $800-900 total.

It should also get better gas mileage than the 350 EFI. 10-18 MPG


Option 3

I want to do this one the most but I don't know if it would be worth the cost and time. I can get a complete good running 12V cummins with 270,000 for $2,700. But I would have to get a different trans or Find the parts to adapt it to the cummins. It's a 95 NV4500 so it has the same gearing same first gear as the cummins so it would be easy to swap the input shaft. Then I would have to find a bell housing mill it down and redrill the bottom Bolt holes. My only concern is modifying the input shaft retainer. I can't seem to find a thread with pics and that go into detail on how it is done. It would probably cost around $3,700 Minus me selling the stock engine and junk 4 speed trans and the chevy NV4500 let's say $1,000-1,200. If I do the conversion to the trans it would still cost about same as selling and buying a different trans $3,700. So around $3000 total after selling the engine and junk trans..

It would also get the best gas mileage out of the 3 18-30 MPG

Cost and MPG may vary, but that is about what it would be.

So its $900 vs $3000

I know the cummins is the better engine, more durable, more power and better gas mileage to weight of the truck. But the price difference is huge and I don't know if I will use it enough to justify the cost. But at the weight of the truck 7-8k and it will probably go up as I want to add a lot of tools and equipment. I just don't know if the 6.2 will handle the weight of the truck.

Something to think about.

The truck as it sits has a 17 foot bed I plan on bobbing it and making the dovetail removible giving me a 12 foot bed making the truck more manageable and useful. With that said I will still only drive it a few times a month.

Starting next year I plan on buying some property and moving across country. This truck will getting used a lot next year during moving. I will also use it to haul equipment to clear land on the property.

Pic of the truck before restoration.


Last edited by jarrodblake; 06-22-2018 at 01:55 AM.
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Old 06-22-2018, 10:29 AM   #2
viking427
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Re: I need some advice on which swap I should do. To get better MPG for the money. C3

I'd pony up the dough and go straight to a 6bt for your planned usage. It'll save you the money, labor and time of re-engineering the drivetrain later. You'll be ahead on the learning curve in building & tuning the 6bt for your truck as well, rather than starting all over when you decide you're not happy with either gas or 6.2.
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Old 06-22-2018, 04:45 PM   #3
DieselSJ
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Re: I need some advice on which swap I should do. To get better MPG for the money. C3

If you go the route of the 6bt, they can be found with NV4500's attached and you won't need to do any machining.

The 6.2/6.5 will bolt in. HX35 is a great turbo for those and can easily get you into the 250hp/500tq range, which is better than a stock 12v Cummins. Head studs and some good gaskets and you are good to go.
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Old 06-26-2018, 08:02 PM   #4
Dieselwrencher
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Re: I need some advice on which swap I should do. To get better MPG for the money. C3

My .02 cents is to just go with a 12v and not even mess with the 6.2/6.5. Yes it will be more work and maybe more money but it will be way better in the long run.
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Old 06-29-2018, 03:00 AM   #5
jarrodblake
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Re: I need some advice on which swap I should do. To get better MPG for the money. C3

After reading thread after thread on the 6.2 and 6.5 engine destroying themselves I decided not to go with the 6.2.

I ordered a first gen 12V last week should be here monday or tuesday!
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