The Stovebolt Site Forums The Shop Area Engine Shop replace gas with diesel?

Hi folks,

I'm beginning to restore a 67 GMC...it has a "910" logo on the side of the truck and I'm pretty sure the engine size is a 1500.
Can I replace this engine with a 6.2 diesel and still use the same tranny?

Many thanks from a newbie,

Rick

Hy Rick, 910 is a 1/2 ton designation, is the engine an inline six or a V8, what transmission does it currently have? You should be able to use what's there but I think a four speed would be better with a diesel than a three speed, if it's an automatic you will have to deal with the fact that there is no vacuum available for shift modulation.

Thans for your quick response!

The engine is a V8 and because the rocker covers are orange, I'm told it's a 283. It's also got a "three on the tree" transmission.

Just to confirm...you think the 6.2L diesel would be a clean replacement for the current engine?

Thanks,

Rick

Hy again Rick, I have never owned or driven a truck with a 6.2L diesel, so I have no basis to make a comment. This particular chassis never was equipped with this engine as far as I'm aware, so there will be mounting issues to deal with, and I'm not sure if existing bellhousings will accept your transmission, but I suspect they probably will. That being said do you still want to proceed with the swap?

The 6.2 is a good engine for light trucks. It bolts up to the same bell housing. It uses 454 engine mounts so I doubt if that would be a problem. It was never used in 1/2 ton trucks though. It would be awfully heavy on the front end. I don.t think I would do it unless I had a 3/4 or 1 ton.

Hello,
The 6.2 was avail. in 1/2 tons in the 80's. It will bolt up to your GMC bellhousing ok, and the motor mts are the same a V8. But there are some other problems that need to be addressed. The diesel needs a big radiator with an oil cooler. You might be able to use one out of a diesel equipped truck but measure first as they are very long. You will need a very strong starter and there may be a problem with the clutch cross shaft ball stud mounting. If I can find solutions to these problems I might put a 6.2 or 6.5 in my 66 C30. Good luck, Mike

Thanks for your responses! You've been REALLY helpful!
As I keep an eye open for an engine, I'll start to recondition the brakes and shocks. Will I need to replace the coil springs if it's been sitting for 17 years? I'm told they have a memory and will snap. What about the brake master cylinder...any chance it's still ok?
Thanks, Rick

I think you better do more than keep an eye out for an engine. The suggestions graygander gave you will get you as far as setting the engine in the frame. The wiring harnesses have several differences and these are systems that you are going to have to educate yourself about.
Your '67 has manual steering and manual drum brakes?
You're adding a lot of weight that is going to make it a lot harder to steer and to stop. You'll have to use a Hydro-vac for the brakes and that's a conversion project in itself.
The only sensible way to do this conversion would be to buy a complete running truck that you can drive around for a few days. That way you can make sure everything is working that you are going to need and you are going to need everything.
Finding a good unmolested 6.2 truck is going to be the search of a lifetime. Half that you will find have been molested and the other half will have the diesel replaced with a gas engine years ago. Finding the engine alone would be the beginning of a big head ache unless you are one very smart and resourceful cookie.
If you really want to do it, I'd shoot for an early '90s 6.5 Turbo at a minimum. You want this conversion to be interesting, don't you? Problem with that is that you also have to get a '70s or '80s truck for the Disc brake/steering parts. The 6.2s were easily able to tear up the automatics of the time. They were probably the TH400, if I remember. The 6.5 might have the 4R80 with overdrive.
This is starting to sound like a great truck.

RickRoos,

Your project sounds like it gets bigger everytime you blink.

You have received alot of great input and identified some other items which need attention.

Get you plan together and then don't try to eat the whole "whale" at once. just proceed one bite at a time and before you know it your project will turn out great.

Sounds like a fun project.

I look forward to hearing about your progress.

I have been toying with the Idea of putting a duramax/allison combination into one of my project trucks.

enjoy the journey

Yikes! It's getting hairy...but I'm not deterred. My interest in this project has a lot of force behind it and I'm going for it. You should see this thing...light blue and nice to look at. Hopefully nice to drive one day too.

How do I find out about the wiring harness differences?

R

6.2 liters, by the way, is 380 cubic inches, not 283. I thought I heard the 6.2 diesel is basically a 396 block, but I'm not sure about that. Unless the factory used thicker sleeves than the 396 cube gasoline version, the displacement still doesn't match.

Anyway, big difference between a 283 and a 396 block.

I did some research on this conversionm into my '68 c10. Most of the info here is accurate, but a couple other things to consider.The approximate weight of the 6.2 is same as a big block, and using the big block mounts will work. 6.2's were used in half ton trucks, but only the "C" version of the engine with egr mounted in the intake. "C"=light duty, "J" code= heavy duty. "J"'s were used in 3/4 and one ton applications, make better h.p. and have beefier heads, injectors, and cranks. Find a "J" code for your project if you can. The suggestion of finding a running, complete donor for the hyrdo boost brake system with it's master cylinder, prop valve, radiator, etc, is best. If you find a truck from the '82-'87 vintage, you will be able to use the all the front crossmember goodies you want to swap over.

Getting back to the original question of using original tranny, at the very least you need to swap the torque converter and governor to match the diesel, as it has more torque, and runs at much lower rpm, so the shift points are different. As a personal observation, all of the diesel TC's I've ever seen, from factory, are painted diesel alpine green.
Finally, the 6.2L is 379 c.i.d. The "J" mated to a SM465 in my daily driver for the past five years is still a strong runner at 231K on the clock, and gets 21 mpg all day long, when I'm not towing something. And I just bought a '88 G30 van/schoolbus with a "J" in it for conversion to an RV. I have two "C" code spares on stands in the garage. I'm not an expert, but I love the NA6.2 diesel.
Lots of good info at www.dieselplace.com/forum/index.php

HTH, and good luck with it, let us know how it goes.