Best Diesel/Gas Engine?

[jhiggy94]

I am trying to look into an engine swap into my 72 k20. Right now it still has the original 350 in it. I am looking into the best engine for my needs. The main thing i want is to have decent gas mileage with the older truck to make it into a possible better daily driver/hauler. I know with a diesel i can hope for mid 20's mpg? But i also know that a diesel will be very expensive. I am just trying to get the best bang for my buck. Any opinions would be greatly appreciated.

[MARKDTN]

Fuel injection and overdrive trans. There are many options.

TBI with 700R4 or 4L60E
LT1 with 700R4 or 4L60E
TPI with 700R4
Vortec with 4L60E
LS with 4L60E

There are pros and cons with each.

[special-K]

The engine that came in it is hard to bet. You can spend money on an engine with a computer or spend it on gas. And the computer engine you spend money on still takes a good bit of gas anyway.

[gerfunken]

I've decided to throw the 350H.O./SM-465 out and go with a Cummins 5.9 & 47RH. That combo was getting 18-22mpg, but I think it may change slightly with the new application.

[jhiggy94]

did you use a donor truck to get that combo?

[jhiggy94]

Special-k
This is true and i have thought about this a bit. I do plan on swapping out the engine in a couple years once i am able to drive the truck a bit more. I want something that i know will be reliable. Im not sure if i completely trust a 40 year old engine on a everyday basis. Im just trying to find out more information at this point from people who have done it themselves. And also i would prefer to put in an engine that does not have a computer

[jhiggy94]

Has anyone here done it or know of someone who has put a perkins diesel engine in their trucks?

[tmc1986]

i have a 2001 2500 dodge with the 5.9 cummins. i average 22-23 mpgs and can get a solid 25-26 freeway. i have 3.55s so its geared pretty tall. just something to think about, plus it would be cool as hell to put a 5.9 in a classic truck

[gerfunken]

Originally Posted by jhiggy94

did you use a donor truck to get that combo?

Yes, I picked up a '94 dodge 4x4 for a good price. It all goes under the knife in 2 weeks.
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[Vintage Windmills]

Rebuild your 350 and put some vortec heads and intake on it. Or, put a 6.5 in there, bolt in diesel.

[special-K]

I think most of us have considered powertrains that will give us better fuel economy these days,including me. I was just offering another perspective. I'm pretty hung up on turning the wonderfully simple beauty of these trucks into a computer controlled vehicle. You can buy those all day long anywhere. I'm just not ready to own a truck that runs on a computer that I can't analyze,just to have an older looking truck. I can just buy that but with newer styling. Maybe if I lived where I could have my '72 as my only vehicle I'd reconsider. So,that leaves older diesel engines...and overdrive transmissions.

[MARKDTN]

My '83 K20 started life with a 350 and 700R4. It always got 14 mpg city. I swapped to a '91 Corvette TPI engine with the same transmission. Now I get 17 mpg city. I am not at all scared of a computer. I used to be, but not anymore. I think a full-on catestrophic computer failure is rare. It might not run great, but it will still limp in. If you figure fuel at $3.50/gal it used to cost me $250 in fuel to go 1000 miles. Now it costs $206. So I save $44 every 1000 miles. In 23,000 miles it will pay for itself-not to mention that my oil is much cleaner now. That is a real-world example.

[chevy72blu]

Check out the LSX swap section of the board.

I went LS and its the best thing thats ever happened to my truck. The reliability and drive-ability far exceed any carbed motor I've owned and 300 whp while getting 23 MPG is just icing on the cake.

It can be done very cost effectively if you do your homework (I didn't )

[jhiggy94]

Are you getting 23 mpg with a c10? I just have doubts that i would get that performance with a large heavy K20

[Bigdav160]

My Wife and I both have Cummins powered EC 4x4 trucks as DD's.
One is VP(HO) 6 speed the other common rail (HO) automatic (48RE). Both 3.55 geared

Modifications on the trucks are minimal and geared toward fuel economy.

The 6 speed truck gets 19 mpg in my city commute. The automatic gets 16-17 mpg. On the highway they are identical at 20 mpg @ 80 mph. We don't travel long stretches of road where the speed limit is 65 mph or lower so I suspect 23-24 mpg might be possible at those slower speeds.

Recently we went to Colorado and back (2200 miles) in a AWD - 6.2L Cadillac Escalade. Our highway average was 18 mpg @75 mph

If you're still interested there are couple threads on this forum and others about Cummins conversions.

[jhiggy94]

Bigdav160- I would appreciate any information that you have from your two builds. Specifically on the automatic. I think that i am going to be leaning towards this route. Or else a 6.5L Thanks.
Jake

[jhiggy94]

Does anyone know what years i would be looking at for a 12v or a 6.5L to get a mostly mechanical engine without a computer?

[bwright]

Before the 37s, my stock '84 K20 (6.2, 700r4, 3.73) would knock down mid-20s mpg with ease...I haven't checked the MPG since the 6" lift and 37s were added.

Be prepared, the 6.2 is gutless (4.3L V6's had more HP and nearly as much torque).

[Bob B.]

By far the easiest diesel conversion is to use the GM 6.2L or 6.5L. They weigh about the same as a big block, they have the standard Chevy bell housing bolt pattern, and they work well with gasoline engine gearing. It's almost a bolt-in. Plus the engines are very inexpensive, and new crate 6.5L's are still available. They are not real powerful, but they get very good fuel economy.

[jhiggy94]

What year of the 6.5L are the best to use?

[Dieselwrencher]

Originally Posted by jhiggy94

Has anyone here done it or know of someone who has put a perkins diesel engine in their trucks?

A friend of mine from Mexico, Mo has one in a 78 Ford F-350 with an Allison 1000 series 6 speed. It also has compound turbos, and is freaking sweet!

[Dieselwrencher]

Originally Posted by jhiggy94

Does anyone know what years i would be looking at for a 12v mostly mechanical engine without a computer?

94-98 Dodge will be your best bet on a 5.9. The 94-95 for an auto as you can control this trans with 2 pressure switches, or toggle switches. A 5.9 will be more work, but well worth it in the end.

[Bob B.]

Originally Posted by jhiggy94

What year of the 6.5L are the best to use?

Any 6.2 or 6.5 non-turbo will not use a computer. Early 6.5 turbos don't have a computer either. Generally speaking, 6.5's have stronger blocks than the 6.2's. Later is better. Nice thing is a new 6.5 can be built up as a mechanical engine with the right pump and injectors. These guys are the experts:

http://www.62-65-dieselpage.com/