'88 G10

[Dr. Jones]

I have an 88 Chevy fullsize van that I want to convert to a 3/4 or 1 ton diesel with 4 wheel drive I thinking that I'll just set the body on a frame. I was thinking that a '94 or newer dodge would be the way to go, but I'm not sure that I know enough to make that decision. Any suggestions. Oh yeah I also want to eventually run it on biodiesel.

[asavage]

If you wanted 2WD, this would be easy. My family bought new, and I owned for seven years, an '83 G30 w/6.2l diesel. 80k miles, 19.1 MPG avg over that span. The OEM setup workes great. Though I'm not sure whether GM offered the 6.2/6.5l in the 1/2T G-series.

I liked mine a lot. However, I don't know about 4wd.

The Cummins is a loooong engine. And it's not light, either. Good power & economy, though.

Personally, I want to find an Isuzu 3.9l Four from an NPR, and put it in something like a '69 C20.

[Dr. Jones]

Originally I was going to put a chevy diesel in it but heard that ealier Chevy diesels were good to stay away from. I figured that would probably be the easiest frame to mount to mount the body to. You think that the Cummins is long enough to give me some serious problems during the conversion? I like that it is such a proven engine and this vechicles primary use will be a work vechicle (I don't need a 1 ton, 4 wheel drive diesel vechicle to pull my briefcase around, you know what I mean?) Those people really bother me. It pretty much has to be four wheel, cause I'm going to use it to plow snow.


What is a NPR? I like the '69 van.

[asavage]

Opinions vary about the 6.2/6.5l . I had the very first year of production. My father ran it the first 102k miles, and he's a maintenance nut. If anything broke, it got fixed. If something was scheduled to be done, it got done.

I got it ten years old. I drove it hard, but continued the regular maintenance, aided by his notes (for example, he learned to replace the alternator belt EVERY year, because you could get 1.5 yrs out of it, but no more. It ate alternator belts annually.). I had one glow plug die, one water pump, two glow plug controllers replaced in 180k miles (it's a crude device), and a vacuum pump. The fuel lift pump leaked when I got it, so it got a new one (cheap & easy, under $40 for brand new). That's about it. Oil changed regularly, of course, and while I owned it it got synthetic oil as well. It was a very good running engine. It used a quart in 800 miles when I got it, and when I sold it, it used a quart in 1600 miles (synthetic).

Head gasket failures were common on the early 6.2ls. Mine would bubble a bit to the outside when hot.

I'd buy another 6.2l in heartbeat, if I had a need for one. It's a heavy engine, but lighter than my Ford 6.9l or a Cummins 5.9l for that matter.

IIRC, my 6.2l was rated for 160hp (exactly double the LD28). I didn't like that the AT (700-R4) wouldn't do both full throttle and OD at the same time. If floored and given a long enough stretch, it would do 88 MPH in direct (3rd) -- this is a rig with all the aerodynamics of a shoebox! At that speed, the IP's governor was at the RPM limit, and the engine wouldn't rev any higher.

However, I learned that if I backed off the throttle slightly, the trans would then shift to OD, and I could pick up another 4 MPH: 92. That was the "true" top speed.

The engine never leaked any oil.

Towing power wasn't spectacular. I remember towing a '66 MB 230S (dual two-barrel Zenith progressives) on a U-Haul car trailer in Portland and hitting one hill that I could only pull 45 MPH flat out. But generally it had decent power, judged by standards of that era. Nowadays, diesels truckes are not underpowered anymore, they're all common-rail and direct injection and nearly all turbocharged, so it's not fair to compare the two.

On your project: you won't fit the Cummins under the G10 hood, period. Take a look at one sometime. You would have to build a longer doghouse, move the trans back maybe 8-12" or more. The trans for the Cummins is a lot larger than the 700-R4 you've got in there now. I know nothing about the 4wd drivetrain in the front, but unless you use a GM front end, you are talking major mods -- certainly more than I'd want to deal with, even with a complete shop. You'd be way ahead of the game to start with a gasser 4wd van and convert to a similar layout diesel. I don't want to rain on your parade, I've just done enough of this kind of thing to get tired thinking about it

[Dr. Jones]

Ouch.

[asavage]

Didn't GM offer 4WD in the G-series at one time? If so, the 6.2l bolts up to the TH400 and 700-R4 (though the internals are different, and you definitely want at least the diesel torque converter), and can use the SBC motor mounts. It's practically a bolt-in conversion between the 5.7l gasser and the 6.2l diesel, from what I've read.

The hard part is finding the GM 4WD stuff to fit under the G10. If you can't use at least some bolt-in, you'll be redesigning suspension AND steering AND plumbing AND wiring all at the same time -- more that I personally would want to tackle. But nothing's impossible. I've recently read about using a Buick 3.8l V6 fuel injection system to convert a Slant Six engine to MPI, and the article was very well written, made me want to try it on a Corvair.

[goglio704]

A TH400 will bolt up to a 6.2, but the TH400 is a vacuum modulated tranny, and I could be wrong but I don't think GM ever mated them. There is an aftermarket device that will replace the vacuum modulator with a cable to the throttle, but I could never make it work right with a TH350 (also vacuum modulated) mated to a (don't laugh) 5.7 diesel. This was a factory combo and they achieved the variable vacuum with a little regulating valve (rare and expensive) that bolted to the side of the IP and varied the vacuum with the throttle.

[asavage]

The GM VRV worked rather well with the TH400 and 5.7l diesel. I know, my boss bought the first one: 1978 C10, red stripped-down model w/5.7l diesel. I had to service it and occasionally drive it. We used it to tow a tandem-axle trailer with a Bobcat on it. In Fall of 1977.

Next year, he bought a luxo model '79 C10 (Scottsdale) diesel with velour interiour and power windows and all. That one had the VRV fail, and I bypassed it for a couple of weeks while the dealer got me another one.

I've had a couple over the years, and the VRV never gave me any trouble. Got what looks to be the same damned part on my '84 F20 diesel (6.9l & C6). Works well there, too. I've never had another one fail, except that one on the '79 C10 in early 1980.

I imagine that adapting a VRV to the 6.2l wouldn't be so difficult. I've only ever seen the 6.2l with a 700-R4 behind it, but I've heard of the TH400 behind one. I think it was an option for some HD rigs.

[goglio704]

The "VRV" did work well - way better than the cable rig. I only had one fail - one of the vacuum lines simply snapped off the darn thing. If you had one on a Ford it makes me wonder if it may be a Lucas, CAV, Stanadyne part? rather than a GM. The glow plug controller for the 5.7 could be bought from Lucas - way cheaper than GM. I seem to recall getting soaked in excess of 100 bucks for the VRV.