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Need help with a plan

D

DwarF

1/2 ton status
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Austin, Tx
Gas prices going up, emissions controls going up, I can read the writing on the walls....

I have a 350 crate (350+ hp), 700R4, np241 and 4.56 gears, one ton axles and drive line.

Currently, I have the truck torn down to frame. No electrics, no fuel lines, no fuel tank. I was considering going efi for gas mileage, but I think I could invest the same money (selling some of my current components) and get a diesel. It is a daily driver, and I am not going to be doing any heavy duty towing. I want the increased mileage and torque of efi. It seems like the best possible time to swap to diesel, so i wanted yall's input on what I should do. The truck was diesel when I started, so I have the larger radiator, hydroboost, etc.

I was thinking a cummings 6bt, with a new torque converter. I have no fuel pump or fuel lines/tanke/sending unit currently. Am I on the right track? Additional insights?

Please advise,
 
If you're not gonna be doing any heavy towing I'd consider a 6.2. You'll never be able to sell your stuff for near enough money to do a Cummin's swap, but finding a decent 6.2 for reasonable money is easy...plus it just drops in.

I did this exact swap, but my truck was never a diesel previously and I haven't regretted it for a minute.

Mine is also a DD and my mileage went from 8-10 mpg with my carb'd 355 to 16+ mpg with the 6.2. With a 700R-4 you should be able to squeak out 20 mpg with no trouble.

My two cents...

Rene
 
I thought the 6.2 was under powered, couldn't get a turbo for it, Not peppy, etc. I do have access to one for very cheap, but I would want to rebuild it. If I am doing a ground up, is this really the best engine to start with?

What about the 6.5TD?
 
Yes, they are slow and underpowered when compared to, say, a duramax. Compared to the motors of its day it was not a bad motor on the numbers page. It was not designed to be a heavy duty motor, but a more efficient alternative. Im happy with mine, it does everything i need it too.

Mine continuously gets me above 20 MPG, recording a best of over 25mpg. That was mixed highway/city driving with a 700R4, 3.73's and 33' BFG's. Had some stanadyne performance formula in at that time as well. It will never be a torque monster like the cummins could be, but with the Sidewinder kit from Banks, it will put out well 400 ft-lbs. If i remember correctly when one of the off-road rags installed one it dyno'd at 471 ft-lbs at the rear wheels. This includes the torque converter raising those numbers, but its still not bad.
 
6.2 would be easy, and cheaper. If you're looking for mainly mpg, aren't going to tow much weight, and want to keep it cheap, that's probably the way to go. I've heard of some great mpg numbers from 6.2's.

Cummins motors don't come cheap, and it would be a custom swap, not a GM part bolt-in. Typical prices run about $3K for a used first gen engine. Usually more for the P pump engines. The plus of the Cummins is the torque (600 lb. ft. easily with simple, cheap mods) and long, long life.
 
I agree. After doing a lot of reading, I think my decision is down to 6.5L vs 6.2L.

Right now, I am leaning toward a 93 manual injection 6.5L, and swapping out my torque converter, and either running bigger tires or selling my 4.56 gears.

What about this plan?
 
Sounds like a good plan to me /forums/images/graemlins/waytogo.gif

As far as being underpowered, I have no trouble breaking my 40's loose on wettish pavement. That's something my 350 would never do. Outright acceleration is very similar to my old 350.

Rene
 
Is there a difference in the direct and indirect inject between these two?
 
If you're asking about the 6.2L vs. 6.5L, both are indirect injection engines. Instead of the injectors pointing directly into the cylinders, they point into a pre-combustion chamber, allowing for a better swirling action of the air-fuel mixture. The pre-cups allow for a better fuel mileage engine, but I do believe they restrict power somewhat.

The Cummins is a direct-injection engine.

The 6.2L and 6.5L are virtually identical, sharing many of the same parts, same camshaft, crankshaft, balancer, etc. You can even swap heads and injection pumps from one to the other. The only real difference between the two is a larger bore on the 6.5L, and coated pistons on the turbo model. Of course there are some minor fuel system differences between the two, as well as head designs and that sort of thing.

The 6.2L was designed first, and the 6.5L is just a better, later model.

Casey
 
Wow, thanks for the response guys, those are some pretty comprehensive answers. I have a few more questions though.

First, if I get naturally aspirated, and later goto a Banks Tubo, will this fit nicely without modification to the AC unit on the firewall?

Lastly, is there anything else to be aware of before I get started? Wiring harnesses, TV cable differences, any of those kind of gotchas I need to be aware of for my budgeting?

Thanks again for the advice
 
Banks is a direct bolt-on, no other mods required.

It would be easiest to start with a complete donor truck if you could. It's all those little things that nickel and dime you to death. You'll need a radiator, alternator, ps pump, a/c compressor brackets and possibly the compressor (if so desired), starter, air cleaner, basically everything on the engine. It doesn't really share anything with a gasser except the bellhousing pattern and the motor mounts.

Yep, TV cable is different as well. If you can find an old, worn out 6.2L powered truck, you can swap everything over, put your gasser in the other truck, and sell it to get back a few of your dollars.

Casey
 
I have one that was diesel and converted to gas. So I have the hydroboost, pumps, etc. I don't have the starter or TV though. /forums/images/graemlins/thinking.gif
 
Throttle cable is quite different too. I used a complete running donor pig and raped all the bits and pieces off of it, then sold the shell to U2Slow (Kevin).

I unplugged the engine bay wiring harness from the firewall side of the fuse block and plugged in the diesel harness for a very clean and factory appearing install. I'd have to say that is about the easiest way to do it.

I went a step further and swapped the underdash stuff and the gauge cluster while I was at it...which got me the correct 'dash' with the "Diesel fuel only' gas guage and the glow plug light. You'll also need the second battery tray.

It's a little labor intensive, but you said your truck is currently apart anyways so it sounds like half the work is already done.

Rene
 
I have no direct experience with the 6.5, except that a friend had one and liked it pretty well until it hit about 100K miles. Then it started having continuous problems. Things like the injection pump, starter, head gasket, etc. He bailed out of that truck shortly after that. Maybe it was a fluke or lemon, I don't know.

Sounds like a good project though. I've always thought of building a Blazer or Ramcharger with a Cummins and 1-ton drivetrain. There are a few out there already.

At one time, I had thought of running a 6.2 or 6.5 in my Jeep. The deciding factor was the noise. I like being able to talk from rig to rig on the trail without yelling over the diesel. So, I run a diesel in the tow rig, and a quiet gasser in the Jeep. /forums/images/graemlins/waytogo.gif
 
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