By Request: Cummins powered '71 Pictures

[TP from Cntl PA]

Here are some pictures of my '71 C-20 that I repowered with a "Whimpy" Cummins, or a 210 CI 6AT3.4 Turbo'ed 6 cylinder. Planned on starting to tear it apart for paint after using it this past spring and summer on the farm, but with fuel prices the way they are I think that will wait as we have ALOT of fire wood to haul with it and my '69 GMC 1-ton. I learned alot from this one and I am already planning on building my next one with a 4x4 2-ton IH Loadstar frame, 4-53 2 stroke Jimmy, 9 spd Roadranger, and of-course using a '69 GMC cab and front clip

For what I have in this project, I can't complain with what it is. Plan on painting the cab and front clip the OEM dark green instead of that lighter green/white two tone that is on it now, with a black stake body of-course if I can ever actually stop using it to finish it.........

[junkyardjohn]

VERY NICE... VERY NICE INDEED. JOHN

[FUNMUDDER]

Looks like a good working/sleeper truck. Pretty sweet you stuffed a Cummins in there . Sure is a lot different than the B-series I've been around. But I just have to ask, WHY A DETRIOT 4-53 IN A JIMMY?????????????????? Detriot diesels are way too loud, at least the old 53 and 71 series. Your crazy, but I like the way you think . People who are different are cool, especially when it come to vehicles.
Jake

[Jim_PA]

Add this to the "how do I improve my gas mileage" thread

38 MPG is almost unbelievable!! Good job.

P.S. Nice battery tie-down

[4x4Poet]

I'm considering throwing a CTD in my K20 burb, so I have a few questions:

1. How is the noise level inside the cab with the windows rolled up? Any sound deadener?
2. Noise level in cab with windows down.?
3. Noise level standing next to grill with hood down?

4. Did you use a 67-72 radiator or a Dodge rad? Or other app? Custom?
5. Fan? Shroud?

6. What tranny did you run and what bellhousing app?
7. Clutch type and size to handle that torque?
8. Transfer case?
9. OEM tranny crossmember?

10. Firewall clearance issues?
11. Vacuum for brakes solution?
12. Is the front D44 housing plenty strong for that CTD weight (what? ~1100lbs?)

Well, that's more than a few. Sorry. And thanks. Feel free to refer me to a previous thread.

[67_C-30]

Very cool! How does the 6AT3.4 compare in size to a 5.9 Cummins (out a of Dodge)? I think I remember reading that they were smaller in physical size, but I'm not positive. I wanted to do a Cummins swap on my '67 C-30 , but I found a 12,000 mile 6.2 out of a Hummer and I am turbo charging it. It will be a much easier swap for me since I have 2 other parts trucks with 6.2's that I can rob parts from. I am planning on painting the engine the old Detroit Diesel green since it was designed by Detroit for GM anyway. I am making a custom pressure chamber to use with a non EGR 6.2 intake instead of using the 6.5 intake. I am making the chamber out a 71 Porsche oil bath air cleaner (of all things!?!) It has a really cool look, and will make the engine appear older. I'm planning on the painting the entire engine the old Detroit Diesel green (since it was designed by Detroit for GM anyway) like they did on Diesel trucks of that era, and like they still do on equipment and some big truck diesels now. I think the look of engine with everything painted that drab green contrasting with fresh black firewall and inner fenders will make it look huge under the hood. The 6.5 Turbo's look very wide as it is even in black, so a green on stuffed under the hood of my '67 will look cool.

[special-K]

Good questions,4x4poet.I`ve been waiting to see this done.What motor is it exactly?And,how`s the power?Have you driven a 6.2 before so you can compare?

[1969 GMC]

That truck is a 2wd.
Also, the engine is 3.4 liters displacement , so I'm go out on a limb here and say its smaller than a B series. ALso, these never came in dodge trucks...thats just the 5.9

[Russell]

I still wanna see how you got that second transmission in there backwards to act like an overdrive unit

[TP from Cntl PA]

Like I said, it ain't pretty..........And I didn't want to bend up nice stainless hardlines for that booster so I had extra hydraulic hoses in the shed that I pie-pieced together so I had brakes...........Going from the vacuum booster to that hydro-booster is unreal. We had to apply decent pressure with our foot with the vacuum booster, this one, if you just touch it, it nearly throws you against the steering wheel.

Battery tie down is custom

I'll try to answer the questions, by 4x4 poet in the order he asked, then finish up with the other ones.

1. I have this one straight piped from the turbo to a ugly stack behind the headache rack on the drivers side(where its smoking from). Inside the truck with the windows up(Even with a small hole in the floor) it is considerably quieter than the 350 I pulled out that was equiped with a very muffling muffler. You actaully can't even hear it running at all.
2. Noise is pretty loud with the windows down with that stack, this engine has a tiny turbo, but makes as much noise as a straight piped BIG CAM Cummins(In OTR trucks) on hard excellaration, and at idle all you hear is the whistling.
3 Just hear the normal diesel rattle, although NOTHING like a newer 5.9 at idle
4. Chevy truck 4 core radiator
5. I have an electric pusher fan on it now, I will need one a bit bigger but that is nothing hard to change.
6. You won't believe it, but SM326(I think) Saginaw that was behind the 350, with another one mounted behind it in reverse for a totally of 10 forward gears that gives me gear splits and 2 Overdrive ratios..........I know everyone says they are weak, but we've had nearly nothing but them on the farm and we've been unable to break them. Don't shock load them and they'll do whatever you ask them. Didn't want a granny 4-spd as I don't like the sloppyness in them, and the HD NV's were too expensive as I didn't know if this swap would actually work...........I actually only have $1200 in the engine swap............
7. It has an adapter on it for GM's 12" flywheel and has GM's common bell housing bolt pattern.
8. 4x2
9. Non needed with the 3spd
10. If I did it over again, I'd move it back towards the firewall...........It's in the stock location for a SB, but clearance on the front end is a bit tight.
11. Hydraulic Booster from later model GM pickup with a 6.2..........Runs off the powersteering pump and works very well.
12. The weight of these engines is a killer on the 4x2 suspension, although that could easily be fixed on a 4x4 with helpers or heavier spring packs. I plan on swapping in HD 1-ton front springs or air bagging it in the future. This engine comes in close to 900 lbs and has a bottom end that would probably survive a small atomic bomb going off in the oil pan, and that 900 lbs is on the limit of the suspension capabilities.......Main reason I didn't go with a 6BTA5.9

Engine differences:
6BTA5.9 or know as the 5.9: 360 Cubes Industrial/truck engine(Don't know hp ratings)
my engine 6AT3.4: 210 Cubes Industrial Engine Only(Mines making about 150 hp)

Russell, I'll see what I can do.........

I ripped a 350 out to replace it with this, After having it and using it on the farm..........I don't miss the SBC one bit!

[TP from Cntl PA]

FM:...........I always had a fond spot for 2 stroke Detroits, if you keep them full of oil, it is tough to break them. My next one will be built to pull a gooseneck trailer to haul farm equipment. For the weight and size, Detroits make the most power IMO.

Most people didn't like them because they didn't know how to drive them, you have to slam your hand in the door when you get in the truck and they run very well.............Had a farm truck with a 6-71 and I've seen guys lug the h*ll out of it, and of-course it didn't run well at all. When we run it, it was hammer down, and you shifted to keep it there, and it would blow the other IH(Same model) off the road, and that was packing a 555 Cummins.

[special-K]

Alot of cranes run detroits and they love being wound out.Like you said,get`em up and keep`em up.They can run all day like that.With 150hp you have 15 over a 6.2.What do I pull one from?Are these the bread truck motors(StepVan)?

[67ChevyRedneck]

38 mpg??? WOW!!! Want to sell it I'm still confused on how the tranny(s) work. Is there two shifters in the cab? Do you have to have the back one in first, go through the first one's gears, and then shift the second tranny into second, and then for back to the fisrt again.... Saginaws are just 3 speeds, right? How would you have a double overdrive...isn't the final gear ratio still 1:1? However it works that's awesome. If I had the cash I'd send my truck up to you for a retrofit

[TP from Cntl PA]

67-Yes, they are 3spds that for general use work quite well, and their is two 3 spd shifters on the floor. You can drive it, 1st, 3rd then 1st, 2nd, and then 1st, 1st and then bump up to 2nd and go through it again, then 3rd and when you get to 3, 2 your up to 65 and cruising down the highway. Granted that splitting is alot of work. So we usually go through 1,2,3 on the first one, then put the second one up into 2nd, so your at 3,2 and cruising.
The overdrive is obtained by the second transmission being mounted A$$ backwards, or the input shaft is the output and the two transmissions are connected tail shaft to tail shaft by putting two u-joint yokes together. Of-course, it doesn't shift as smooth as it normally would if you just clutch and shift.............We are used to big trucks, so we just double clutch and it drops right in.

Special K, these were originally generator engines, and were retro-fitted into break trucks from my understanding.............Mine came from some sort of delievery truck, don't know for sure, I bought it on a stand.

If anyone of you are considering doing this, I'd look into a 4BT3.9 or the 4 cylinder version of the ones in the dodges..........I wanted a 6 to show off, but parts for mine aren't as common as the 4 and 6BT.

[67_C-30]

Originally Posted by TP from Cntl PA

67-Yes, they are 3spds that for general use work quite well, and their is two 3 spd shifters on the floor. You can drive it, 1st, 3rd then 1st, 2nd, and then 1st, 1st and then bump up to 2nd and go through it again, then 3rd and when you get to 3, 2 your up to 65 and cruising down the highway. Granted that splitting is alot of work. So we usually go through 1,2,3 on the first one, then put the second one up into 2nd, so your at 3,2 and cruising.
The overdrive is obtained by the second transmission being mounted A$$ backwards, or the input shaft is the output and the two transmissions are connected tail shaft to tail shaft by putting two u-joint yokes together. Of-course, it doesn't shift as smooth as it normally would if you just clutch and shift.............We are used to big trucks, so we just double clutch and it drops right in.

Special K, these were originally generator engines, and were retro-fitted into break trucks from my understanding.............Mine came from some sort of delievery truck, don't know for sure, I bought it on a stand.

If anyone of you are considering doing this, I'd look into a 4BT3.9 or the 4 cylinder version of the ones in the dodges..........I wanted a 6 to show off, but parts for mine aren't as common as the 4 and 6BT.

How is the driveshaft connected to the input shaft coming out of the backwards tranny? Is this a special or custom made yoke, or is there something readily available?

[TP from Cntl PA]

This truck had the two piece driveshaft.............So I cut the small one, and measured the outside diameter, and then the inside diameter and then found out how thick the wall was on the tubing...........Using my trusty South Bend Lathe, I cut a grove in the center piece of an old clutch so the shaft would fit tightly in it so it was centered up, then I welded it to the driveshaft.

Anyone who is a bit knowledgeable with a lathe/welder could easily throw one of these setups together. Although not as nice as a Gear Vendors setup, it was ALOT cheaper than the $3K they quoted me for a kit for my truck.

I am going to take the setup out soon to do an inspection and replace some internally parts in the transmission that were questionable on the one I started with(Teeth on acouple gears were wearing weird), So I'll get some better pictures.

[sneakysnake]

Originally Posted by TP from Cntl PA

This truck had the two piece driveshaft.............So I cut the small one, and measured the outside diameter, and then the inside diameter and then found out how thick the wall was on the tubing...........Using my trusty South Bend Lathe, I cut a grove in the center piece of an old clutch so the shaft would fit tightly in it so it was centered up, then I welded it to the driveshaft.

Anyone who is a bit knowledgeable with a lathe/welder could easily throw one of these setups together. Although not as nice as a Gear Vendors setup, it was ALOT cheaper than the $3K they quoted me for a kit for my truck.

I am going to take the setup out soon to do an inspection and replace some internally parts in the transmission that were questionable on the one I started with(Teeth on acouple gears were wearing weird), So I'll get some better pictures.

I like your style.

[TP from Cntl PA]

Here is the shifter setup in the truck............Two 3spd cheap Mr. Gasket 3 spd floor shifters that I bought for $15.00 on ebay. Works good for us though.


You can see they work pretty good with the new(er) seats too.

[69TowRig]

Originally Posted by TP from Cntl PA

...and the two transmissions are connected tail shaft to tail shaft by putting two u-joint yokes together.

So you put the slip-yokes together or you have a CV in there? I'd think there would be some degree of vibration if you just had the two slip yokes joined with a u-joint.

Very cool setup. I'd really like HALF of that 38 mpg in either of my trucks!

[toms68cst]

That set up is wild. I love it. All we need now is a sound clip!

[wolfthing2000]

I realy like this idea! Would I expect the same mileage without the over driving tranny in reverse that you describe, runnin with a SM420 and transfercase in a 4-wheel drive Jeep truck with 4.56 final drive and 36 inch rubber???? ( this is a future project slaighted for a 307 small block, but could change).
What is the going price for an engine like this????

[TP from Cntl PA]

Originally Posted by wolfthing2000

I realy like this idea! Would I expect the same mileage without the over driving tranny in reverse that you describe, runnin with a SM420 and transfercase in a 4-wheel drive Jeep truck with 4.56 final drive and 36 inch rubber???? ( this is a future project slaighted for a 307 small block, but could change).
What is the going price for an engine like this????

I gave $1200 for the engine, when I decided whether to build up another 350 SBC to replace the one in it, or go this route, I decided to do this.............This engine was rebuilt not to long before I bought it, or so I was told.

You can get a 4BT3.9 for $1000 and up too.

[wolfthing2000]

So would I expect to get 38 MPG without the overdrive set up?????

[TP from Cntl PA]

Originally Posted by wolfthing2000

So would I expect to get 38 MPG without the overdrive set up?????

Don't know, If your not pulling anything serious, you might get close with a high rear end ratio as long as you have a low first gear to get moving. Diesels are more efficient the closer you get to idle.

[Russell]

Nope, thats where he is getting those kind of milage numbers from. The standard tranny would provide a far steeper overdrive ratio than any conventional overdrive transmission would.

Even a 6.2 will net 22 mpg on the highway, however, this one has that extra steep overdrive, along with the stronger engine (cummins is far more powerful than a 6.2 is stock) so it'll lug better at a lower RPM than the 6.2. All this equals up to the 38 mpg on the highway number