Best diesel 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.

[Ackattack]

I would say a 1st gen 12V cummins for max economy. They have the VE injection pump which I believe will adjust the timing, increasing fuel efficiency. The VE pump won't make as much power as the p-pumped 12V, but can still make good power.

The p-pump 12V will also get decent mileage and put out some power if you know what you're doing.

After that you get into the electronic diesels such as the 24V cummins, common rail cummins, duramax. IMHO with those engines the expense goes up and the reliability goes down. I know when I was looking at what diesel truck I wanted, I looked at earlier duramaxs and when I saw they had injector issues that required replacement at a cost of ~$2k I said no thanks. I believe the 24V have problems with thier injection pumps going out occasionally (again ~$2k).

I would avoid the 6.2L and 6.4L diesels. Just not worth the hassle. I can't say much about the powerstroke engines as they weren't a consideration for me. I think the 7.3L are OK, but there is a reason why there are a lot of "Fummins" out there.

The other part to consider is the tranny. Pretty much, stick with a tranny that came behind a diesel if you want it to live. To get an auto to live behind a hopped up diesel, you're talking big money. I went with a 5 speed mainly to avoid the auto tranny rebuild costs, though my clutch wasn't exactly cheap.

So I ended up buying a running 94 dodge 3/4t 4x4, test drove it a few months while I got a truck to put the cummins in and gathered some parts.

Good luck man, I don't think you'll be disappointed.

[chevy88]

I would say go with cummins also if your looking for mpg and hauling. But only a 6.2 na if you just wanted mileage and a cheap diesel, but ackattack is right cummins all the way for towing part. But do a lot of research the 6.5 diesel will tow and is cheaper than a cummins but doesn't have the reliability of the cummins.
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[Ziegelsteinfaust]

What about Fords or International's IDI engines. I know they are not up to the Cummins power reputation, but they are supposed to be just as reliable. With good mpg too if tuned right.

I found a nice 82 with a 6.9, 5 speed, and in a RCLB. My thoughts were to drop it, and convert it to rcsb. But my knowledge of Diesel is none, and I didn't want to climb up hill on my DD.

[Ziegelsteinfaust]

Have you thought about getting a M1028 CUCV, and dropping your body on it?

They have GM's 6.2 Diesel, and all the good factory 4x4 stuff. In my area they cost $3500, and its an esy of a swap as it gets.

[jhiggy94]

Have any of you guys ever looked at national power supply? It seems like a cool place to get a practically new diesel engine. But prices seem fairly high. Any opinions?

[jhiggy94]

I would also say after reading this and doing a little research my choice would be between a first gen cummins 12v or a 6.5. What transmissions provide the best dependability/usability with these engines? I would prefer to stay with an automatic. Dont get me wrong i love playing around with a five speed. But for everyday driving they seem to get kind of old.

[jhiggy94]

Does anyone know what years i would be looking at for these two motors to get a mostly mechanical engine without a computer?

[6BT 56]

Hi Jhiggy .

Check out my build some time . I recomend the 5.9. Just find a complete 89 to 93 ram and take it's gutz. Thats how i did mine . There are a few guys who did the 6.2 route as well. I was going to do that if I had to cut any tin on my 56. Turns out the 5.9 fit quite well.

[84chevyguyid]

I have an 87 suburban that started out life with a 6.2, when the motor got tired I swapped in a 6.5 with a banks turbo setup and at the same time had the 700 built/beefed up and I really like how it runs now. I always thought when the time comes that the 6.5 gets tired I would probably swap in a gas motor but after fixing up an 87 blazer a year ago with a stock 350 gasser, there is no way I would go with a gas motor in the sub. The 6.5 runs circles around the blazer and I can get almost 5 mpg better with the 6.5 than the 350 gasser. I am building an 86 crew cab with a 12 valve cummins with an allison behind it but it will be another year before its on the road so I cant offer an opinion on that just yet.

[clinebarger]

The old VE & P-7100 6BT diesels are very good engines, But are getting old & when they get old/high mileage they leak oil. Re-seal before installing it.


Common Rail diesels are capable of even better MPG...Tuning is the key to getting there.