72 C20 Cummins/5spd swap build thread

[j_cst_10]

I have posted my previous 70' C10 cummins swap but never really put any detail or a lot of picture in the thread.

What I am going to do now is try and be a little more detailed on the swap since I pulled my c10 apart and am going to transfer the swap over to my newly acquired 72 C20 factory 402/TH400 air conditioned truck.

So essentially I am doing the swap all over again, but this time I know the parts I made will work since my previous truck was a running/driving truck. I also know the proper order of operations so it will make this thread go smoother than when I was first figuring out what/how to do it.

This is me towing home the truck in the fall. Pretty scary ride back, the engine is not in the truck and it made for some poorly distributed trailer weightt

[j_cst_10]

First order of business is to pull the interior, front clip, steering column, brake booster and pedal assembly, transmission crossmember, and front frame brace (this will be put back in later, but it needs to be out of the way for now).

Shown in the picture below is an engine mount that I made. It allows the use of the factory diesel engine mounts.

I made these by mocking the engine in place and fabricating them out of 1/4" steel. Mocking the engine in place is a pain because of the immense engine weight, makes moving it around a chore.



I had to slot the crossmember to frame support factory bracket (found on C20's, not C10's) and bolted them on top of the motor plates I made. This required 4 extended grade 8 bolts to due to my motor plate being sandwiched between.

[j_cst_10]

More to follow but this is where I am at currently. Next the engine will go in place. I am hoping that the high hump floor will give me enough clearance to not have to cut the floor up.

On my C10, it had the low hump floor and I ended up cutting a larger hole then needed to get the trans/bellhousing to fit, mainly due to struggling with 1,500lbs of engine and transmission and getting hung up on every bend and crease in the low hump floor.

I plan on busting the cab mounts loose and temporarily placing a 2x4 in between the cab and frame to give me a little clearance. Once the engine is sitting in I will lower the cab down and hopefully clear. If not, I will figure it out later.

[Dieselwrencher]

Your new C20 looks to be a really nice truck! I'm looking forward to your new build!

[j_cst_10]

The truck is pretty nice, it was originally from Colorado and the sheet metal is in pretty solid condition. It has a lot of minor dings and dents all the way around it, but my plans are to just clean it up for now and drive it. That way I don't have to worry about it getting dinged or scratched.

I have the complete big block set up out of the truck so once this thing is done I'll be looking for something to use all those parts in.

Hopefully by the end of this weekend I will have the engine and trans in and can update this thread again.

[j_cst_10]

I made some progress, although not terribly exciting.

The factory fuel lines run down the passenger side frame rail and need to be relocated to the driver side. On my other truck I just bent some simple lines up, but on this truck all of the lines (brake and fuel) were original and untouched to I wanted to try and re-use them and create a factory appearing set up.

With some tweaking I was able to re-use the fuel lines and transfer them over to the driver side using all of the original brackets and existing holes in the frame to mount them.

The lines are going to be terminated around the front shock mount location so from there forward they don't matter and will be cut off later.

[1972RedNeck]

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[j_cst_10]

I put the engine and trans in the other day. It is quite a handful and requires all kind of impromptu ways to get thing lined up. It helps to have some ratchet straps and a couple floor jacks.

The first thing I did was loosen the cab mounts and sandwich wood in between the frame and the floor to give me extra room. This helps because there isn't a whole lot of room to deal with.




Then came the fun part. I probably spent the better part of an hour wrestling with it. Because of the tight room, it's easier to get the engine in by removing the motor mount on the passenger side of the engine and installing it when the engine is sitting approximately where it is supposed to be.











[URL=http://s549.photobucket.com/user/jt158805/media/IMG_2362.jpg.html][/URL}

[j_cst_10]

I lowered the cab down and I have a slight clearance issue. The very top of the trans tunnel is resting on the bell housing. It is so close that I am going to purchase a new set of cab mounts and see if that gives me enough room.



Also, for a transmission crossmember I had an aftermarket 4 spd crossmember laying around that I was able to use. When I measured my driveshaft angle I was able to use a piece of 2x4 steel to mate the rubber mount to the getrag 5 spd. I will have to re-evaluate this since the ride height and rear end are different than the other truck I had this set up in. More on the driveshaft and the carrier bearing mount later when I get to putting it in this truck.

[j_cst_10]

For the clutch actuation I chose to go with the factory hydraulic set up found on 89-83 Dodge diesel trucks.

I measured the factory pedal throw and welded a tab to the 67-72 manual pedal set I had for this project. The red bracket is the factory bracket off of an 89-83 Dodge truck that the clutch master twists and locks into from the engine side of the firewall.

For mock up purposes I made an adjustable link to get the right length for the rod that I had to make. The rod/link that comes with the clutch master wont work as it is too short.



Notice how even the bracket appears to line up with the pedal assembly. I definitely lucked out that the pedal geometry was able to be adapted to this particular hydraulic clutch set up. All of the parts used will be factory Dodge or Chevy parts.



Next it was time to cut a hole in the firewall. Using a 2 3/8" hole saw I cut a clearance hole for the clutch master to go through.



And here is a picture looking through the hole with the pedal assembly installed. I will get a picture with the clutch master and power booster installed so you can see how it fits up.

[j_cst_10]

[6BT 56]

Looks great. That's very similar to how I did my hyd clutch on my 56. Same dodge parts bracket etc. just mine are under the floor to work with my orriginal pedal configuration . Keep up the great work .

[Dieselwrencher]

Nice work, it's looking great!

[colgad]

Did you change the front springs? How much did the frontend drop?
You make the swap look easy, great work!!!!

[j_cst_10]

Haha yeah I made it look easy because I did it twice. The first go around was with my ratty C10, then ended up pulling that truck apart and transferring my work to this '72 C20. Things usually come out nicer the second time.

As for springs, I bought a set at rock auto from an old thread I found on here. My truck was a factory big block truck but the front end still came down a good bit with the stock springs. I replaced them with Moog #6454 about $80 from rock auto.

The truck sits great and rides really well, almost level but slightly nose down which is where I wanted it. Below is an updated pic with it sitting right (keep in mind the truck has a 1' body lift to clear the drivetrain).

[COS399]

nice job.

[colgad]

Great info, thanks so much. Is there room for the AC compressor?

[j_cst_10]

No room for the AC compressor in stock position with a 2wd crossmember in place. The frame had to be cut away significantly (I tried on my other truck). However, you can find a non AC belt and it works with the normal accessory drive minus the compressor.

[colgad]

Do you think there would be room for the AC compressor if in a leaf spring style frame? I am looking at a 12v for my C50 but here in Tampa AC is must.

[j_cst_10]

Yeah I here that, my aunt has a condo near st Pete, was just down in April. I think it might be possible but it would be tight and require some trimming.

I spent a good deal of time trying to position the engine with the compressor in place prior to making my mounts and it was just to cumbersome so I removed it and then went ahead.

I lucked out and my mounts that I fabricated are absolutely dead on, I think if I went back and tried to make it work with the compressor now I would be able to finagle it.

[j_cst_10]

So I would give it a maybe. With a 4wd front end and subsequent lack of 2wd crossmember I think you could drop the motor low enough to not have a problem with the compressor position.

[colgad]

Originally Posted by j_cst_10

So I would give it a maybe. With a 4wd front end and subsequent lack of 2wd crossmember I think you could drop the motor low enough to not have a problem with the compressor position.

OK, good that gives me enough hope to give it a try. I want a 12v with 5 speed. So I will start the search after the power tour.
Thanks again

[1972RedNeck]

Originally Posted by colgad

OK, good that gives me enough hope to give it a try. I want a 12v with 5 speed. So I will start the search after the power tour.
Thanks again

No way will A/C compressor fit in the frame. You need a "mid mount" compressor bracket and then it works great.

[andrewhagler]

Did you keep the stock fuel tank or did you install an aftermarket unit?

[j_cst_10]

I was through this old thread and saw that I never had posted any pictures of the truck fully completed. Below are some pictures I snapped of it before winter. I had the front and rear bumper from my 1970 CST so I stuck them on since the truck previously had a fabricated step bumper and a smashed front bumper.

I relocated the turn signals behind the front grill (not pictured), turned out pretty nice.