72 GMC Longbed Duramax Swap

[NathenMyers]

While we pulled the Carpet out of the Cab, we found this "seed" receipt, or certificate from 1972!

then we cut the floor out so that the Cab would sit down over the allison using an air grinder

[NathenMyers]

and finally sat the Cab down over everything.


i swear the engine sits like it's SUPPOSED to be in there.

We can see that we're going to have to move the fuel filter to another location, and we might end up shaving some of the heater core cover just to help make a little more room.

but! it's on there!

We were both AWFULLY excited saturday evening!

Me ( i hold the flashlight) in the black hoodie, Arlie ( the real mechanic) in gray.

[71blksuper4x4]

Looking good Nathan. Trevor

[Dieselwrencher]

Very nice! I bet you're getting stoked to drive it!

[Orange67]

Great job, looking good! Do you know if a stock high hump trans tunnel will work? Or do you have to fabricate one?

[feller]

Awesome, I'm gonna have to come see it.

[NathenMyers]

Hey guys!!

ok, update, but no pictures. Also! a couple questions!

I drove from Louisville to Hicksville, OH to visit "Hicksville Auto Recyclers" (facebook page: https://www.facebook.com/HicksvilleA...yclers?fref=ts) for some help with my transmission issues. They said that they do 2WD to 4WD Conversions all the time, it's also where i got my 2WD tailshaft and housing. I arrived and was blown away by this establishment.

Fellas i'll tell you what, that place was super awesome. it was a building probably... same size as your standard Kroger. Basically it's an indoor JunkYard. They deal pretty much exclusively in Duramax truck parts. I saw probably...30 engines, and probably twice that in transmissions and transfer cases just sitting on shelves. Rows and Rows of misc other parts.

they said a duramax rearend will run me about $750. The cheapest I've found elsewhere is closer to 1500.

I got to talk to one of their engine dudes, and he really helped me with some questions on wiring that i had.

I pulled the Allison out of the trunk of my car, and Jake "Stu" Sterwart helped me. It turns out. I'm ignorant, and the transmission guy that I took it to at home just had no idea what was going on inside of an Allison. Because Stu just set everything i had together, tightened it down, and boom. Everything was put together properly. I had all of the parts that i required, i just couldn't get them to fit quite correctly!

Got it home, and this weekend got the torque converter in it, and the tranny connected to the engine. So now, everything is in it.

I have to build the tranny hump. Put the doghouse on. and get the Cab (with all of the wiring) from the duramax parts truck from the junkyard next weekend.

Now my questions!

1. When you guys moved the gas tank out of the cab, What kind of fuel cell did you guys get? Did you guys just get one from LMC and call it good?

2. Those of you that have done Duramax Swaps, what did you guys do for Fuel pumps? Since i'm not using a tank/pump set up from the Parts truck, what did you guys do about your pump? also, do you guys know what kind of fuel pressure i would need? (forgive me if these are a couple ignorant questions. i figured i would start here and then move on if none of you guys had an answer off the top of your heads)

3. I can get the steering column from the parts truck, but i hate the look of a new style steering column and wheel in an old cab. Ideas? i recognize that it's my project, and it feels lazy to ask! but, of you guys that already did a Duramax swap, what's somethign that you did, that if you were doing it again, you WOULDNT do?

Thanks guys!!!i appreciate your suggestions and help!!

[joel.e]

1. When you guys moved the gas tank out of the cab, What kind of fuel cell did you guys get? Did you guys just get one from LMC and call it good?

I used the Boyd's Welding tank and added a "draw straw"


2. Those of you that have done Duramax Swaps, what did you guys do for Fuel pumps? Since i'm not using a tank/pump set up from the Parts truck, what did you guys do about your pump? also, do you guys know what kind of fuel pressure i would need? (forgive me if these are a couple ignorant questions. i figured i would start here and then move on if none of you guys had an answer off the top of your heads)

You don't need a fuel pump. The CP3 will pull the fuel from the tank. You will need one if you turn it up but the stock truck doesn't have one.


3. I can get the steering column from the parts truck, but i hate the look of a new style steering column and wheel in an old cab. Ideas? i recognize that it's my project, and it feels lazy to ask! but, of you guys that already did a Duramax swap, what's somethign that you did, that if you were doing it again, you WOULDNT do?

Why not use the stock column?? Is something in the way?

[NathenMyers]

Thanks!

The truck is originally a 3 spd manual transmission, and i 'm switching to Auto. From what i understand I'm going to need an auto steering column so that the shifters and everything line up correctly. Am I wrong?

I think that I must have been mistaken about the pumps. I thought that a stock Dmax had a pump in the tank, and an Injector pump that was connected to the cam gear. and that THOSE were what it ran on. Since my truck doesnt have an "in tank" pump, then i would need to add an in line pump or something to take the place of the in tank one.

as far as things in the way. So far i'm flabbergasted at how well the dmax sits in this truck!

thanks for the input!

[gerfunken]

Originally Posted by NathenMyers

1. When you guys moved the gas tank out of the cab, What kind of fuel cell did you guys get? Did you guys just get one from LMC and call it good?

After a couple of measurements, I found that the 30 gal. fuel tank from a square body suburban fits nicely where the spare tire in the '72 would sit.

I decided to go with the square-body suburban 31 gallon gas tank. That required a little bit of fabrication on the back end of the truck.

To start, the rear cross-sill (the one with the light plug) came out, and was rotated 180-degrees, and became the front brace for the fuel tank.




This effort was followed for quite some time with lots of measurements. I needed to have the fuel neck clear the frame, but at the same time not be so tall as it would bump into the bottom of the bed. Likewise, I needed to play with it front-to-back as so to sit between the bed rails. Once that was done, I finished the calculations and made the brackets.







Then it was a matter of getting it into its final resting place.

[joel.e]

The high pressure pump is enough to pull the fuel on a stock configuration. I know the early Dmax didnt' have a lift pump and we have a 2012 LML at work and it doesn't either.

Gotcha on the 3 speed column. My truck was auto so I just used that and rigged a Lokar cable to make it work.

[Dieselwrencher]

The cp3s on most dmaxes have lift pumps built on them. Isuzu does this on a lot of their engines. There might be some dmax models that don't have the built in lift pumps, but I can't remember which they are. I've put a couple air dogs on to help for winter drivability. If you're keeping it fairly stock, you should b fine with relying on your stock cp3 lift pump.

[burnin oil]

I would add a lift pump. Stock many if not all chevys did not have fuel pumps. On the other hand all the Dodges with CP3s have a lift pump. Most if not all of the dual feed kits for the Cummins motors run the second CP3 from a lift pump. This second pump is usually from a Duramax. Moral of the story is you are building so you might as well do it once and it is ready if you ever want more power. Loosing fuel pressure on a diesel causes all kinds of headaches! My 72 has a 73+ blazer tank in it and it works well and holds 31 gallons. I did flip it around to keep the filler on the drivers side and ran the filler up next to the stake body on the inside of the bed. It should be pretty easy to modify the sending unit for a diesel. That's my plan for when I eventually swap the Cummins in.

[NathenMyers]

Oh man you guys! thank you so much for the help!
I'm going to have to start researching lift pumps now!


also, burnin oil, is there any chance you could put up a picture of your stake pocket fuel filler please?!?

thanks again guys!

[burnin oil]

Its not in the pocket. I cut a hole through the bed and stuck a pipe up through it. Its functional but nothing pretty to look at. I have not rebuilt my bed yet so I just run what I brung so to say. As far as the pipe a cheap way to do it is to get an exhaust shop to bend up a piece of pipe and swage the end to fit the cap part off of a donor. Its only soldered into the gas filler. Quick and easy way to install it.

[NathenMyers]

Awesome! thanks!

After doin some lookin', i think i'm actually going to go with a 69 Camaro Tank, and put the filler behind the license plate. I feel like that's a nice balance between "cool" and "easy" haha

Just talked to the junk yard folks today! this weekend i'm getting the Cab from the duramax truck, so that i can get the wiring and such outta there!

Also the Rearend from the Duramax as well!

Stuff's happenin' in southern indiana fellas!

[NathenMyers]

All this talk about Fuel pumps and such made me realize that ya'll were speaking Greek to me!

Today has been a day of learnin'!

now that i've read up on WHAT CP3 pumps and Lift pumps are/do. I realized that CP3 pumps are a gear driven pump ON the duramax engine itself. In it's stock form, this will do me fine. NOW i understand what Joel.e was telling me!

I'm going to look into some lift pumps. But may hold off until next year. Right now my goal is to get this baby on the road, and yonder budget is shrinking. a 500 dollar lift pump would go a long way somewhere else.

i really can't thank everyone enough for all of your suggestions and info. This forum is a Godsend.

[Dieselwrencher]

Nothing wrong with waiting. But it can be a pita later to install one. For instance if you get a 150gph unit, you have to drop the tank and a draw straw. No fun after you start driving your truck from a long build.

[feller]

When I had my Cummins, I was having lift pump issues so instead of buying a $500 one, I decided to go cheap and put a holley blue pump on the frame rail it worked for about a year and a half or two. Probably not the best way to do things, but cheaper and fixed my issues. Without regulator it was giving me about 14 psi

[burnin oil]

Splitting hairs but a 31 gallon tank is a blazer tank and what I run. The 40-42 gallon was the large suburban tank and has the same basic dimensions but deeper. You should really like the tank in there along with the nice range it will provide. My dodge had a 35 gallon tank and I typically went 650 miles per tank unloaded. Keep up the good work.

To help out on the fuel pump deal here is the basics. A lift pump is what is typically called a fuel pump on a gasser. Its basic purpose is to get fuel up to the motor. Once fuel as at the motor it goes to an injection pump that boosts the pressure and sends it to the injectors. I don't know the specifics for a Dmax but the fuel pressure to the injectors can hit the 20,000-30,000psi range under some driving conditions. This high pressure in the injector rail can easily destroy injector nozzles, think sandblasting action, so make sure you incorporate a good fuel filter that is atleast 7 micron. With all this going on it is why I suggest going with a lift pump. Starving a diesel for fuel will cause a loss of power and actually decrease power. In general the air needs mean nothing to a diesel, its the fuel that makes power. There needs to be air in there to burn the fuel and help cool the pistons but the fuel ratio is not that important.

[burnin oil]

one more thing I forgot to mention. Most injection pumps are cooled by the fuel being pumped through them. If all the fuel is being burnt there is very little extra fuel being circulated through the pump to cool it.

[NathenMyers]

Hey everyone!
it's been a few weeks! Dumb old Drill weekend! followed by a weekend trip to Memphis with my wife!

However, this weekend we finally got time to work!

I got the Cab of the 05 Donor truck. Stripped the interior out of it. Seats, all of the plastic and dash ( no instrument cluster) radio, and doors! Steering Column (air bag intact) and passenger airbag! All of it's for sale if anyone's lookin!

After that was stripped, We pulled all of the in-cab wiring harness out, but, whoever bought the instrument cluster out of the junkyard just cut all of the wiring so that they could pull the cluster.

I sat down to try to start soldering the cut wires together, however, there are a LOT of wires that are the same color AND same gauge. So, i'm going to try to price a another junkyard in-cab harness that hasnt been screwed up. if that ends up being way to expensive. I might just go ahead and try to repair this one first.

While i was doing that King Mechanic Arlie was putting the 05 rearend under my 72 truck for me. That thing is HUGE. Also, it turns out this newer rearend is around an inch wider on each side. but from what we can tell it will still fit under the rear fenders of the stock bed. which, if we backspace the wheels correctly, will still look ok!

Another weekend in the bag!

[chrapladm]

Wwow.....looks great so far.

Just hearing about the town of Salem brings back many childhood memories.

[NathenMyers]

Hey Guys! It's been a few weeks! We had a vacation, a couple drill weekends, a national holiday, and one lazy weekend between postings!

First, we've started getting the 69 Camaro tank in position, i'm basically following this: http://67-72chevytrucks.com/vboard/s...d.php?t=448431 Build thread. I'll have some better pictures of MY stuff in a couple weekends, we got caught up in the DOING of it to take pictures, haha.

I put the new brakes and calipers on the Duramax Rear end that we put in.

Arlie, the mechanic of the two of us, works at a county garage in town, and had to replace the brake system in one of their dump trucks. He started figuring and looking at the Hydro Boost system.

and that dude has made it work. we have to get a block made to mount the master cylinder to the hydraboost. and i'll put up better pictures of that next time also.

That's most of what we've gotten done in the last 5 weeks or so!

next on the agenda,
master cylinder mounted
get the fuel tank plumbed so that i can connect it to the duramax fuel lines.
run brake lines!

[COS399]

Glad to see it is coming along. How many gallons does that fuel tank hold?