GMC truck

[DRDEATH]

This is kind of off the wall but I thought I would post here for guidence. I have a 1999 GMC 4 x 4 1 ton truck. Other than the paint it is in great shape. It has a 454 in it and I would like to change it for either a GMC diesel or a Dodge Cummins diesel. Who out there has any knowledge about this? Also is there any problems with Big Brother ( government ) in doing something like this. The reason for this is I have an unlimited supply of UMO to burn. Thanks, DD

[Apogee]

If you do it, you want one of the late AM General blocks.  Otherwise it's a waste of time imho...

http://www.6-5liter.com/

Some states require you to fill out paperwork regarding the conversion, others don't.  Just have to check where you live...

Short of that, it's a direct bolt-in in your truck.

Steve

[Ronmar]

Do you have to pass emissions with that truck?  If so, it won't pass anymore with a radically modified engine compartment:). I also hear road tests are becomming more commonplace.  If they dip your tank and you are not burning taxed road diesel(using the roads without paying the tax) you will be fined...  The french fry exhaust smell is a real giveaway:).  I have read a few different stories of states going after individuals for tax evasion and producing fuel without a liscence.  You can google this subject for more reading.  I guess it depends on where you are located and how intrusive big brother is in your life.  Just something to think about...

[JohnF]

I've had a bunch of GM diesels, most of them are not very good.  Essentially (apart from the DMax) they are a converted 350 GM gas engine with marginal tolerances for the higher compression.

If you can, do a convert to a Cummins 5.9, great engine but it is a difficult conversion, especially in a 4 x 4.  I know one guy put a Cummins in his Hummer, it took him hundreds of hours.

As usual - for simplicity, the GM diesel would be best, for longevity you need to do a bit of work!

[vdubnut62]

DRDEATH,  This is the world as I understand it.The GM diesel is very weak in the older configuration that you would have to use, unless you wanted to change the wiring harness and ECM out of a computer controlled truck. Then the newer units have some sort of optical sensor that has to "see" through the fuel, so that precludes the use of UMO or a mix thereof, presumably to keep contaminants out of the exhaust catalyst/afterburner.
To go with the Cummins, a late 97 and up is computer controlled with a very sensitive rotary style pump that won't stand the use of UMO.
the early years also have the same pump, but not ECM controlled. 97's and  back a few years use a Bosch P-7100 inline pump that will do the job. If your truck has an automatic tranny, it will not stand up to the Cummins, although the SAE bellhousings are available to fit darn near anything, but they are not cheap! My choice would be an Allison, if you want to stay with the auto. Ask MobilBob his opinion
Simply put, if you want to burn UMO, it would be much easier AND cheaper to just trade trucks.

[bschwartz]

John,

The earlier attempts at a diesel were a modified 350.  The 6.5 (and earlier 6.2) are a detroit engine.  Not too powerful, but not prone to the same head/gasket issues that the earlier motors suffered from.

The optical sensor is only on the later computer controlled versions.
The 6.2 and 6.5 turbo were mechanical injection till around '91 or '92.  They run quite well on UMO.  I can dump just about anything into my 6.2 powered '83 Suburban, and it just motors down the road just fine.  Just don't expect a ton of power.
My '95 Suburban with the computer controlled 6.5 does get a clearer fuel to avoid problems (WVO).

[bschwartz]

Oh and on the longevity scale, my '95 has 205,500 miles so far.  No it isn't a Cummins, but if you don't need the power, they work and are cheap  to purchase, run and buy replacement parts for.

[vdubnut62]

If you are set on a 6.2, Russell at Flint hills diesel had one left. Humvee takeout with 20k miles or so $500.

http://www.flinthillsdiesel.com/

Ron

[Apogee]

Mike,

At the very least, you want the AM General heads.  All of the others eventually crack.

You want the later block with the 10mm head bolts that prevents #8 from cracking.

You will also want to run studs rather than the stretch-once head bolts the factory used.  ARP makes them for this application.

The non-computerized injection pump was used through 1993.

AM General/GM finally got the 6.5 right for the Humvees.  They added molybdenum to the metal mix on the blocks and heads and eliminated the cracking issues.

Agreed that the Cummins swap would be the way to go.  However, it will be LOTS more work.  The turbo 400 in your truck will take the torque as long as it's in decent condition.  If it's one of the 4 speed automatics, look out because they're not as strong.

Steve

[bschwartz]

I would expect the 1999 truck to have a 4L80E 4speed overdrive trans.  It is stronger than the old 700R4 that it replaced.  They also used a 4L60E that wasn't near as stout, but I don't think you'll find one in a 1 ton.
The 4L80E holds up just fine behind a 6.5, but I doubt it would last long behind a cummins.

The head cracking was also a bigger problem before '97 when they changed cooling to a dual thermostat.

Yes, mechanical injection was used till '93 in pickups.  They went to electronic earlier in suburbans for some reason.

I guess a lot of this really depends on what you are expecting the truck to do once you are done.

[JohnF]

If you must go GM, go for the 6.2, they are very tolerant of alternate fuels.  As for going to AMG heads to prevent cracking - waste of time, I've had 2 AMG heads crack in my Hummer  If you are worried about #8 cracking (not a problem that I know of in the 6.2) put in a head cooling kit, they are readily available.  Good thing about the 6.2's is that they take very little hp to run themselves, so you can harvest most of the output.

The Cummins is a bear to retrofit into a GM, better off buying a Dodge to start with!

[d34]

To go with the Cummins, a late 97 and up is computer controlled with a very sensitive rotary style pump that won't stand the use of UMO.

98.5 is when the change happened. That also is when they went from 12 valve to the 24 valve.

[vdubnut62]

To go with the Cummins, a late 97 and up is computer controlled with a very sensitive rotary style pump that won't stand the use of UMO.

98.5 is when the change happened. That also is when they went from 12 valve to the 24 valve.

Absolutely right, I stand corrected.
Ron

[mobile_bob]

if your truck has an auto, and has a vacuum modulator it will have to be replaced by a cable type TV unit
if your truck has a computer controlled automatic, who knows what will have to be done to make it work.

for my money, i would never attempt such a project, most times these conversions turn out to be a real cluster or crap.
that is unless you use a gm diesel then maybe it will work out.

another thing to consider is whether or not your fuel tank is galvanized steel, if so it will have to be replaced
diesel and galvanized tanks are a bad mix. in any case you will need to provide for a fuel return.

for the money and time i think you will find that going out and buying a newer truck that has a diesel already will be cheaper
in the long run.

far better to find an old diesel mini truck like a datsun or toyota and run the wheels off of it with your alternate fuels in my opinion
and leave the chevy for doing heavy intermittent work it was designed to do.

my opinion only, ymmv
but there are few times that engine swaps like this work out , however
i once swapped out a 440 mopar/727 torqueflight with a 455 buick/turbo 400 in an afternoon into a '78 two wheel drive 3/4 ton p/u
that was an amazing fit, where everything fit like a glove, rad hoses, p/s hoses, ujoint, throttle cable, etc. all went like a dream
the only thing i had to provide as two towers for the front engine mounts and move the rear crossmember, twist the shift cross linkage
180 degree's and adapt the exhaust pipes which turned out to be the same size too.

that was a good swap, and i later even grafted the gm frigidaire compressor to the dodge ac system

on the other hand stuffing a 472 cadillac into my 55 chevy 210 was a nightmare!

i don't even want to think about the issues relating to the transmission and transfer case you are contemplating.

think long and hard before you bite off this project

bob g

[Henry W]

Hi DD,

If I was going to haul things long distances I might consider one of the small flat bed or box trucks with a lift gate like an Isuzu NPR, Nissan (UD), Hino, Mits Fuso, ect. You can get them very cheap and they are simple to work on.

Here is an example.

http://kalamazoo.craigslist.org/ctd/1886636817.html

Henry