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Author Topic: 12v Cummins Swap/'73 GMC 2500  (Read 15453 times)

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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #50 on: December 15, 2019, 11:07:46 PM »
I have access to 2 Ford 32s, but driver's drop. No bueno.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #51 on: December 15, 2019, 11:23:17 PM »
I have access to 2 Ford 32s, but driver's drop. No bueno.

Pull the input and bore the gm case to fit
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Offline America.Mike

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #52 on: December 16, 2019, 12:07:46 AM »
   I rebuilt the dodge nv4500 case and installed a Chevy 32 spline mainshaft.


  With my transfer case and doubler I bored the NP205 case  for a 90mm big bearing. Im  installing a ford 31 spline input a  cut resplined and heat treated  mainshaft for the NP203 and a 32spline input.


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Offline America.Mike

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12v Cummins Swap/'73 GMC 2500
« Reply #53 on: December 16, 2019, 12:09:46 AM »
Trucks going to be sweet when done.


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« Last Edit: December 16, 2019, 12:18:21 AM by America.Mike »

Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #54 on: December 16, 2019, 07:21:39 AM »
I have access to 2 Ford 32s, but driver's drop. No bueno.

might want to recount.. i think they’re 31 spline and short input. you’d need a 32 spline long from a chevy behind a TH400 or 4L80 i believe.

which kit are you thinking of using?

that gray case i have started out as a small bore. couple hours at the machine shop and now it’s a big bore lol

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #55 on: December 16, 2019, 08:21:36 AM »
You guys are making my head hurt.
I think you're right Seth, 31 spline now that I think about it.
I like the doubler idea, but this truck won't get used much. She's semi retired to a much easier life now. .. only need 4wd to pull Don out of the mulch beds when he comes to visit.
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #56 on: December 16, 2019, 08:28:22 AM »
that’s a pretty sweet kit actually. shortens up drive train length some (not that you need it in SCLB square body..) and reduces pieces used.

if you do run across a 29 spline dodge case, they bolt right up to the 4500. did it for the kaiser. where exactly are you located? out by turner?

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #57 on: December 16, 2019, 08:36:31 AM »
I'm thinking with that kit I should be able to reuse the stock Chevy single stick without hitting my bench seat. As it is, looks like the nv4500 stick is going to move back about 3-4 inches farther towards the seat. I don't really want to have to use a remote twin stick at this time.... also don't want bucket seats.
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #58 on: December 16, 2019, 09:54:47 AM »
I'm thinking with that kit I should be able to reuse the stock Chevy single stick without hitting my bench seat. As it is, looks like the nv4500 stick is going to move back about 3-4 inches farther towards the seat. I don't really want to have to use a remote twin stick at this time.... also don't want bucket seats.

well.. if you get to that point, i have a set of JB fab shifter and some short cables if you need. can sell cheap ish (not MSRP..  :rolleyes: ) thanks to another member on here..

Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #59 on: December 16, 2019, 10:25:44 AM »
I'm thinking with that kit I should be able to reuse the stock Chevy single stick without hitting my bench seat. As it is, looks like the nv4500 stick is going to move back about 3-4 inches farther towards the seat. I don't really want to have to use a remote twin stick at this time.... also don't want bucket seats.

and if it’s any confirmation.. when we put the 4500 in the kaiser it pushed the shifter back (from original 4 speed) about 4” as well. just for comparison.

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #60 on: December 16, 2019, 01:58:01 PM »
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #61 on: December 16, 2019, 06:40:46 PM »
GM and Dodge shifter angles are different, One is more straight up and down than the other fyi.....
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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #62 on: December 17, 2019, 08:19:18 AM »
GM and Dodge shifter angles are different, One is more straight up and down than the other fyi.....

is this for 205s or 4500s?

i can get an angle from a ‘99 dodge NV4500 and report back

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #63 on: December 17, 2019, 08:29:45 AM »
While you guys sort out the shifter angles....

Next up was resealing the t-cover. Good timing on my part, no pun intended. The infamous dowel pin had started it's exodus from the block, and the 4 rear housing screws were fairly loose.
The black piece blocks the dowel from coming out, and the new allen bolt is too long to unscrew by itself, without hitting the outer cover.
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Offline wilsonphil

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #64 on: December 17, 2019, 10:59:30 AM »
I have seen the bolts for the gear case destroy more Cummins than the Dow pin, glad you got to them now, locktite is your friend.

Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #65 on: December 17, 2019, 02:54:28 PM »
GM and Dodge shifter angles are different, One is more straight up and down than the other fyi.....

is this for 205s or 4500s?

i can get an angle from a ‘99 dodge NV4500 and report back

4500's, I have GM if you need but I think the base of the handle could be warmed up and tweaked slightly....
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #66 on: December 26, 2019, 09:48:25 PM »
Finally did an initial mock-up on the engine.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #67 on: December 26, 2019, 09:53:56 PM »
Then pulled it back out to start cutting the sway bar crossmember, and relocating the brake proportioning valve, to clear the harmonic balancer.
I basically cut out 2" vertical, then welded a 1" strip back in as a lip, curved to match the balancer.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #68 on: December 26, 2019, 09:58:32 PM »
...then added some gussets to the front side as well as relocating the valve from the rear to the front. Extended the brake lines and called it good enough.
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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #69 on: December 26, 2019, 10:10:07 PM »
Nice work, seems to be a common thing for the swap.
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Offline Bigdave_185

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #70 on: December 26, 2019, 10:53:10 PM »
Good enough from my house!


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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #71 on: December 27, 2019, 07:33:26 AM »
Looking good Ken. 


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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #72 on: December 28, 2019, 09:26:17 PM »
Built a stout crossmember today. The motor mounts get welded to it, then I'll box everything in once the engine comes back out.
I used some 3/16" walled 2x5 rec tube.
It was cut with a newly acquired band saw that was in pretty bad shape. One of the things I had to do was mill out one of the big pulleys and install brass bushings.
Pics before and after:

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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #73 on: December 28, 2019, 09:27:58 PM »
..the crossmember tacked in place
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #74 on: December 28, 2019, 09:46:02 PM »
Ken, normally you can buy saw parts online pretty reasonable and quick. I used to buy Kalamazoo saw gears all the time, just for reference.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #75 on: December 28, 2019, 09:51:39 PM »
One of the things I was worried about was the turbo contacting the evaporator case. The case in the donor truck was caved in and burnt...so...
I found a used 24v manifold off a medium truck that has a rear turbo mount, so I mocked it up today.

First pic is of the donor truck, before I pulled the engine.
Other pics are of the 24v manifold.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #76 on: December 28, 2019, 09:54:59 PM »
Then for the heck of it, I stuck the original manifold back on, and it has plenty of clearance. Weird, but makes life easier.
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Offline Bigdave_185

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #77 on: December 28, 2019, 10:27:07 PM »
What improvements are there for a 24v vs the 12v besides the turbo location ?

Looks like it has a good bit more mass to it


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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #78 on: December 28, 2019, 10:54:31 PM »
I don't think it would add any noticable performance. The 12v has rectangular exhaust ports and the 24v has round ones, so you actually have to grind them to match the 12v head. One less thing I have to do now if I keep the original.
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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #79 on: December 29, 2019, 07:39:08 AM »
What are you going to use for heat shielding?  Wrap the turbo and shield the evap?


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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #80 on: December 29, 2019, 11:32:15 AM »
I'll throw a blanket on the turbo, wrap the downpipe, and call it a day.
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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #81 on: December 29, 2019, 01:30:48 PM »
Nice progress.
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Offline Flyin6

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #82 on: December 30, 2019, 02:03:12 PM »
looking good

Fast build
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #83 on: January 08, 2020, 08:43:05 PM »
looking good

Fast build
Thank you kindly.

I got distracted with a couple busy weeks at work, which is strange for this time of year, but spent a few minutes on the project.
First, I pulled the engine back out after some measurements. I had originally decided not to replace the side cover gasket because I didn't want to pull the injection pump. This caused me many restless nights.
...so the pump was removed and the side cover gasket replaced:
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #84 on: January 08, 2020, 08:52:36 PM »
Then went against my original plan to leave this engine at the stock 215hp.

First was the upgraded governor springs. This takes the stock rev limit from about 2800 to 4000. Thanks to the internet, this was painless.
You basically remove a 22mm plug in the governor housing, turn the pump to access one set of springs, then rotate the pump shaft 180* to access the second set, and not drop anything inside.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #85 on: January 08, 2020, 08:56:31 PM »
The only pieces you reuse are the outer large springs, the outer spring cup, and the slotted nut. Shims and other springs are left out.
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #86 on: January 08, 2020, 09:04:13 PM »
Then the AFC housing was removed to access and replace the fuel plate. I went with a conservative choice, a #10.

I'm not going into crazy detail on these mods since there's plenty of videos on the net already, and it technically has little to do with the original purpose of this thread.
« Last Edit: January 08, 2020, 09:05:05 PM by KensAuto »
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #87 on: January 08, 2020, 09:07:33 PM »
The old plate for comparison:
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Offline JR

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #88 on: January 08, 2020, 10:22:11 PM »
If its not broke, don't fix it has no place in these forums.

Upgrade, then upgrade some more!

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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #89 on: January 10, 2020, 10:33:36 PM »
The engine is finally ready to install. I had purchased a quart of Cummins beige but I've been told that I have a touch of OCD. If it's black, it makes it harder to see leaks. A normal person would say that is a bad thing, but after turning wrenches for a few years, my thoughts are if you can't see it, it must not be happening.
I did Cerakote the manifold and turbo.

Next up, boxing the frame.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #90 on: January 11, 2020, 07:43:28 AM »
I like it Ken  :likebutton:
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Offline TexasRedNeck

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #91 on: January 11, 2020, 08:41:44 AM »
Nice!


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Offline cruizng

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #92 on: January 11, 2020, 02:04:21 PM »
Great progress. Next!


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Offline swbhobie16

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #93 on: January 11, 2020, 08:27:21 PM »
does that thing run yet?? that’s all anyone here really cares about anyway. hahah

Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #94 on: January 11, 2020, 10:45:00 PM »
does that thing run yet?? that’s all anyone here really cares about anyway. hahah
I'm sure it's capable of running again, but not capable of driving!

Today I cut out the hardest pieces to start boxing the frame. Anyone that's ever worked on an old truck, especially a GM, knows how uneven the stamped frames can be. In this case, the lower part of the c-channel is almost an inch wider than the upper. ..and the left rail doesn't match the right side, so I can't use the same pattern for both sides.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #95 on: January 11, 2020, 10:57:58 PM »
Ken, are you checking tolerances on that motor before installation? As I’m
Doing research I’m trying to plan for my own upcoming process including building a stand for it to facilitate all of that.

Edit: sorry after looking back I now see Phil gave it two thumbs up so you must have checked something.
« Last Edit: January 11, 2020, 11:01:06 PM by stlaser »
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Offline KensAuto

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #96 on: January 12, 2020, 12:00:05 AM »
Bearings were great, but what I didn't show was the scoring in the cylinders. Looks like someone ran it without an air cleaner for a while. Didn't have much blow-by, so I'm gonna run it.
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Offline stlaser

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #97 on: January 12, 2020, 12:07:24 AM »
Bearings were great, but what I didn't show was the scoring in the cylinders. Looks like someone ran it without an air cleaner for a while. Didn't have much blow-by, so I'm gonna run it.

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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #98 on: January 12, 2020, 08:16:26 AM »
Bearings were great, but what I didn't show was the scoring in the cylinders. Looks like someone ran it without an air cleaner for a while. Didn't have much blow-by, so I'm gonna run it.

 :likebutton:

if she’s passes a compression test, i’d say just put some fuel to it and bump the starter and let it ride.


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Re: 12v Cummins Swap/'73 GMC 2500
« Reply #99 on: January 12, 2020, 04:23:23 PM »
Looks to good to run, then you don't see leaks either.
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