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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Diesel Engine Discussion => Topic started by: countryboy279 on November 17, 2013, 03:51:48 AM

Title: gas to diesel swap
Post by: countryboy279 on November 17, 2013, 03:51:48 AM
I have a 1978 gmc k1500 was thinking about swapping the old 350 for a 6.2 diesel.I know some trucks. came with them so would this be a hard swap or would everything. just bolt rught right up
Title: Re: gas to diesel swap
Post by: Irish_Alley on November 17, 2013, 05:37:25 AM
not to discourage you or anything, but why? why a 6.2?
Title: Re: gas to diesel swap
Post by: countryboy279 on November 17, 2013, 09:44:54 PM
What's wrong with a 6.2 I'm not a diesel expert so is there one that would bolt tight up likke the 6.2 i know the 350 diesel is junk so any advice on this would help
Title: Re: gas to diesel swap
Post by: nlauffer on November 18, 2013, 09:00:49 AM
I'm definitely no expert on diesels, but I know there is a long standing debate between the 6.2 and the 6.5.  Right off hand, I can't remember the pros and cons of each.  Probably start off with a search on the diesel motor you want to use first.  You can swap anything in (Cummins or such), but not much will be just bolt in, unless you get the setup from a similar pickup.  Some of the parts that I think might be difficult would be electrical and fuel.  Two very important parts.  These operate different than the gas (distributor, carb, spark plugs vs glow plugs and glow plug controller)  The fuel lines may be different, I don't know.

There have been many swaps from diesel to gas, so I would assume diesel to gas could be done.  And, it may be quite easy.  The more parts you can get from the donor vehicle, the better.
Title: Re: gas to diesel swap
Post by: Captkaos on November 18, 2013, 01:06:50 PM
I am doing this swap on my 1985 K5 Blazer...  You really need a good complete donor.
engine will drop in and bolt up.  You will have to get a diesel torque converter, you will most likely need new exhaust down tubes.  You really need the much bigger diesel radiator and associated brackets and shroud..

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Title: Re: gas to diesel swap
Post by: fitz on November 18, 2013, 07:01:26 PM
  What trans do you have in your truck?
  As far as the electrical, You can run the glow plugs off a manual push button switch. Other than that, the 6.2 just needs 12 volts to the fuel shut of switch on the injector pump.
  Your fuel system will work up to the fuel pump on the motor. You can use the fuel pump that comes on the 6.2 (called a lift pump on a diesel), or run an electric pump.
I would run a spin on fuel filter mounted to  the firewall rather than the box style factors filter set up.
Title: Re: gas to diesel swap
Post by: hatzie on November 18, 2013, 08:31:27 PM
Automatic glow plugs are easy to install using the later integrated controller from 1987-2001 RV & CK trucks.  No reason to burn out sets of plugs with a pushbutton.

If you're using an automatic transmission you'll need the diesel version.  Manual transmission will need the 6.2 diesel flywheel & diesel clutch kit.

The @92 and up intake valley mounted round Stanadyne FM series filter is cleaner looking and easier to service than firewall mounted filters.  Much cleaner fuel line routing and the intake valley is warm and toasty. I have one on all my trucks.  If you buy a 6.x from a T400 CK chassis it'll have the Stanadyne filter on the motor.

On my 76 the injection pump has a fuel cutoff run from the pink HEI coil power connection and low temp timing advance (HPCA).  I used two Mini ISO relays triggered by the glow inhibit sensor.  One relay grounds the glow inhibit pin on the glow plug contactor/controller after the inhibit cuts out. The other feeds the HPCA 12v till the inhibit sensor cuts out.

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Title: Re: gas to diesel swap
Post by: Irish_Alley on November 19, 2013, 11:00:46 PM
What's wrong with a 6.2 I'm not a diesel expert so is there one that would bolt tight up likke the 6.2 i know the 350 diesel is junk so any advice on this would help

im just getting into diesels myself and i didnt know if you knew anything special about the 6.2 lol. but if i was doing a swap i would look into something with a  turbo
Title: Re: gas to diesel swap
Post by: hatzie on November 20, 2013, 04:40:58 AM
The factory GM Turbo system was only on the 93-01 T400 CK chassis.  It will not fit in the CK RV squares.  You'll need a Banks setup for squarebodies.

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Title: Re: gas to diesel swap
Post by: Irish_Alley on November 20, 2013, 06:14:35 AM
why wont the 6.5td fit? besides the ac box, could this be done with a non ac truck?
Title: Re: gas to diesel swap
Post by: hatzie on November 20, 2013, 07:29:18 AM
why wont the 6.5td fit? besides the ac box, could this be done with a non ac truck?
The angle etc of the downpipe and crossover.  It could probably be done without AC using custom pipes.  It'll be a close fit tho.
The banks setup fits with AC on my 76.

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Title: Re: gas to diesel swap
Post by: 454Man on November 20, 2013, 08:08:35 AM
why wont the 6.5td fit? besides the ac box, could this be done with a non ac truck?
The angle etc of the downpipe and crossover.  It could probably be done without AC using custom pipes.  It'll be a close fit tho.
The banks setup fits with AC on my 76.

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Title: Re: gas to diesel swap
Post by: Irish_Alley on November 20, 2013, 10:54:25 PM
so it will fit just need to mod the ac box or get the banks, gotcha
Title: Re: gas to diesel swap
Post by: hatzie on November 21, 2013, 07:01:36 AM
I've read about using an S10 ac box with the GM turbo.  Not sure what's involved.

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Title: Re: gas to diesel swap
Post by: Captkaos on November 21, 2013, 07:23:49 AM
Alternatives are to use a banks manifold.
There is some information here:
http://www.dieselplace.com/forum/63-gm-diesel-engines/21-6-5l-diesel-engine/63016-93-up-6-5td-73-87-body-w-ac-2.html

If you do it please consider documenting it here
Title: Re: gas to diesel swap
Post by: Stewart G Griffin on December 28, 2013, 07:53:29 PM
i thought the 6.2 and 6.5 were the same engine?   Like the 305 and 350 are the same engine.
Title: Re: gas to diesel swap
Post by: Stewart G Griffin on December 28, 2013, 07:58:00 PM
Here is a 6.5 in a corvette:
http://ecomodder.com/forum/showthread.php/corvette-v8-diesel-conversion-40-mpg-us-avg-1128.html

So it seems like it would pretty straightforward provided you knew what exactly was needed---the ancillary parts and pieces.
Title: Re: gas to diesel swap
Post by: hatzie on December 28, 2013, 08:20:26 PM
i thought the 6.2 and 6.5 were the same engine?   Like the 305 and 350 are the same engine.

They are externally. 
The 6.5 after 1992 got a factory turbo system and serpentine accessory belt somewhere near that time. 
The factory turbo is engineered to fit the T400 chassis.  It can probably be modified to fit the CK RV squares but the turbo needs to be mounted closer to the the radiator.



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Title: Re: gas to diesel swap
Post by: Captkaos on December 29, 2013, 09:25:51 AM
The 6.2L and 6.5L are the same motor but the turbo was designed for the 88-98 chassis.  A non-turbo will easily swap.

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Title: Re: gas to diesel swap
Post by: fitz on January 20, 2014, 07:28:58 PM
Around here cummins 6 bt's sell for around $2000. You can buy 6.2 J code motors from Military CUCV'S  for $300-$500 all day long on craigslist.