'72 GMC K25 build 454/4L80e
 

Hi Guys,
I have had several requests to consolidate my K25 build posts into a single build thread, so here we go. I originally bought this truck 3 years ago while I was working on my '55 Chevy gasser (build thread here: http://67-72chevytrucks.com/vboard/s...96#post4324396 ).
The truck had been purchased by a friend of mine who had started to do a little bodywork for paint...that's why my first pics of the truck show it partially disassembled in the paint shop.
The truck had already had a 454/700R4 combo swapped in.
I got the truck over to my shop, and decided to do a full frame off resto with a few upgrades and color change.
Here are a few pics of her when first bought and the most recent.
I have hundreds of pics I will post in the coming days that follow the complete build from frame and suspension mods...drivetrain mods...to body mods.
Casey

Re: '72 GMC K25 build 454/4L80e
 

First things first. Time to pull the 454/700r and clean and paint the frame. I used Easy-Off oven cleaner...about 6 cans...sprayed one evening and let it soak on the frame overnight. The next morning I broke out the rubber gloves, a BBQ pit brush/scraper, and scrubbed the livin' crap out of the frame. After the scrubbing, a quick hose off with water, and dry with an air hose, I was ready for primer and paint.
I have had frames powdercoated in prior builds, but I went with good old Rustoleum on this build....I wanted something I could apply in the barn, and easy to touch-up if scratched. I used several cans of Rustoleum Rust Converter as a primer...2 good coats...then followed with about 3 coats of Rustoleum Satin. I like the results.
Here's some pics of pulling the 454/700r:

Re: '72 GMC K25 build 454/4L80e
 

Here's some pics of cleaning/painting the frame:

Re: '72 GMC K25 build 454/4L80e
 

Some of you sharper eyed readers might have noticed that before cleaning the frame, I had already installed the suburban gas tank and the DIY 4x4 front engine crossmember.
I'll cover those items here.
The suburban tank I bought off ebay. It required a little cutting/welding before it fit properly.

Re: '72 GMC K25 build 454/4L80e
 

DIY 4x4 crossmember

Re: '72 GMC K25 build 454/4L80e
 

Sweet! Love it.

Re: '72 GMC K25 build 454/4L80e
 

Time to rebuild the front and rear suspensions.
I installed a 4" front and rear spring lift kit from ORD...Off Road Designs. It uses new springs/shocks for the front suspension, and a shackle flip kit for the rear suspension to achieve the 4 inches of lift. While I had everything apart, I completely rebuilt the front and rear steering and braking components using stock GM components as well as a Superlift raised steering arm.
Also, I rebuilt the front and rear differentials. The front diff is a stock DANA 44 with 4.10 gears. The factory spicer lockouts were broken, so I installed new WARN lockout hubs.
The rear diff is a factory DANA 60 with 4.10 gears as well. The rear leaf pack is huge, and has a factory swaybar attached...a heavy duty towing setup for sureEverything was removed, sand or media blasted and primed/painted with Rustoleum satin black.

Re: '72 GMC K25 build 454/4L80e
 

More front end pics

Re: '72 GMC K25 build 454/4L80e
 

Some rear suspension pics.

Re: '72 GMC K25 build 454/4L80e
 

I moved the gas tank out of the cab and used a Suburban tank mounted in the rear of the frame. As for the fuel filler, I pie cut the left rear bed stake pocket to mount a stainless boat filler...used the plasma cutter to cut out the bottom portion of the tail light housing, then used a combo of welded stainless u-bends and certified fuel filler hose to route to the fuel tank inlet. I used the vent outlets on the tank...one on each side...to use as vents to help in case the tank was slow to fill. Happy to say that it fills just fine...not slow at all.
Here's some pics:

Re: '72 GMC K25 build 454/4L80e
 

more

Re: '72 GMC K25 build 454/4L80e
 

That's looking awesome!

Re: '72 GMC K25 build 454/4L80e
 

Were there any crossmember modifications necessary to mount the rear trans mount? I'm using a 4l85e in a 69 C-10 with a ZZ-502 and was wondering about crossmember placement and trans mount.
Posted via Mobile Device

Re: '72 GMC K25 build 454/4L80e
 

The trans crossmember had to be moved rearward due to the longer length of the 4L80...not hard to do.
I should have moved the DIY engine crossmember forward an inch. This would have given me more room for the HEI to clear the firewall...as it is now, the HEI is very close to the firewall...even with the 2" body lift.
NOTE: I tell everyone thinking of a 4L80 swap that I would seriously think of using a T400/GearVendors set-up instead. If I had to do it over again, that is what I would do. When you factor in the cost of a rebuilt 4L80/converter/stand alone computer/harness...you are right at the cost of running the gearvendors, and it has 6 speeds and is rated at 1200hp. Plus you don't have to deal with programming issues, etc. Just my 2 cents.
Here's a shot of the assembled drivetrain in the frame.

Re: '72 GMC K25 build 454/4L80e
 

Looking great! What are you you planning on using to control that trans?
Posted via Mobile Device

Re: '72 GMC K25 build 454/4L80e
 

Now the frame, steering, and suspension are mostly done, lets look at the metal work that was done to the cab. I needed to replace both rockers, both cab corners and most of the floorboards and toe boards. How I wish those 1-piece replacemant floors were available 2 years ago when I did this, lol.
Here's some pics:

Re: '72 GMC K25 build 454/4L80e
 

more

Re: '72 GMC K25 build 454/4L80e
 

Now it was time to break out the sand blaster and strip the cab, doors, and core support.

Re: '72 GMC K25 build 454/4L80e
 

After stripping the parts, I hauled everything over to a friends shop to have it covered in etching primer.
Here's some pics of the cab...thought I had pics of the other metal, but can't find them.

Re: '72 GMC K25 build 454/4L80e
 

Thanks c10seconds.
I have a TCI controller and harness. It's mounted in the factory console.
I just haven't got that far yet in this build thread, lol.

Re: '72 GMC K25 build 454/4L80e
 

I sent the cab, fenders, doors, inner fenders, core support and hood to be "cut in". For those that don't know, "cut-in" is where the interior surfaces of the panels are painted...leaving the exterior of the panels unpainted. You then assemble the pieces together and take it back to the paint shop for final finish paint.
Only the cab was painted inside and out.
While these pieces would be gone for a while...months and months, it was time to get to my favorite part of the build...the drivetrain!

Re: '72 GMC K25 build 454/4L80e
 

Let's start with the engine. I had a 454 that came out of another truck I sold. I disassembled the engine, and took the block down to the machine shop where they bored it .060, freshened the crank and rods, installed the main bearings, new pistons/rings, and freeze plugs.
I had a spare set of big port oval '049 heads that I took to the machine shop as well. A 3 angle valve job was performed, as well as cutting the spring pockets for the COMP Cams springs. The heads were then completed with all new COMP pieces.
After bringing everything home, I installed the COMP roller cam, and a new Cloyes double-roller, new Mellings HV oilpump, Edelbrock aluminum waterpump, and finally the heads with ARP bolts.
Then it was time for a nice coat of Chevy orange.

Re: '72 GMC K25 build 454/4L80e
 

It was time to install the new COMP roller lifters, pushrods and roller rockers.
I'm going for a kind of stock performance look for the entire build...kind of like if GM had decided to build an "SS" truck if you will. I like the look of the Chevelle SS engine bay, so I kind of wanted this engine to look like that...factory color, factory style aluminum intake, chrome factory valve covers, factory dual snorkle Corvette air cleaner, factory Chevelle exhaust manifolds, etc.
The Chevelle exhaust manifolds were ground smoothe and ceramic coated. The intake is a polished Edelbrock Performer 2.0. The valvecovers are a "tall" version of factory Corvette big block covers, and even have the stock wire loom holders I will use.

Re: '72 GMC K25 build 454/4L80e
 

Before I could trial fit the engine in the frame, I had to deal with the 4L80-to-NP205 transfer case issue.
Thank goodness for this message board and the internet; without them, I would have never gotten this part of the swap figured out.
I could write a small booklet on what is necessary to do this mod, but here's the quick version of what was necessary.
The 4L80 I used came out of a buddy's 2wd '96 Chevy dually...it had lost reverse gear. I took it to a guy who has built a couple of stout T400's for me, and had him rebuild it with all new hard parts and an RV output shaft. I had to source a hard to find T400-to-NP205 adapter with the older "figure 8" bolt pattern...but this adapter will not bolt to the 4L80 without having the adapter's inner mounting boss "turned down" by a machine shop...so I had that done at a local machine shop.
After all the mods, I was able to mate everything together.
After rebuilding the NP-205, I painted it with a red that was the closest I could find to the factory red.

Re: '72 GMC K25 build 454/4L80e
 

Back when I installed the DIY 4x4 engine crossmember, I became concerned about how close the mock-up engine block was to the relatively narrow frame rails. Even though I was going to run exhaust manifolds and not headers I was worried about clearance issues.
These worries were confirmed when I started to mock up the engine/trans combo.
I bolted the exhaust manifolds to my plastic 454 block and set them in the engine bay...it became clear that the driver's side crossmember would need a little clearancing with a grinder, and the pass side frame rail would have to be trimmed in order for everything to fit.
I used a plasma cutter to trim the pass side rail, then cut a 1/4" piece of plate to "box" the frame.
After everything fit well, a little Rustoleum paint finished it off.

Re: '72 GMC K25 build 454/4L80e
 

frame mod for exhaust pics

Re: '72 GMC K25 build 454/4L80e
 

Now I was able to set the engine in without exhaust clearance issues.

Re: '72 GMC K25 build 454/4L80e
 

With the mock-up block in place, I bolted the 4L80/t-case in place to see where the trans crossmembers would need to be moved rearward to compensate for the 4L80's longer length over the stock T350.

Re: '72 GMC K25 build 454/4L80e
 

The cab, fenders, and core support came back from the paint shop. We set the cab back on the frame, and I assembled the front clip sheetmetal.

Re: '72 GMC K25 build 454/4L80e
 

With the front clip assembled, it was time to work under the hood...install the Alan Grove brkts and engine accessories. Then the custom aluminum radiator/shroud/dual fans. Got the new engine and front light harness installed. Wired up the DUI custom-curved HEI. Installed the new battery tray and wired up the fans/relays behind it. Fabricated a TPS switch swicth mount and accuator for the custom tuned Sean Murphy-built 830cfm quadrajet. Installed the completely restored and replated master cylinder/booster/brackets, as well as the restored heater box. Lots of plumbing and wiring going on, lol.

Re: '72 GMC K25 build 454/4L80e
 

After I installed the new A/C condensor, I was worried it was to "bright" in it's natural aluminum finish and would show through the large grille openings, so I painted it black with radiator paint.

Re: '72 GMC K25 build 454/4L80e
 

With the majority of the underhood stuff done, it was time to turn to the interior. First up was installing the FatMat soundproofing I bought on ebay. I put it all along the firewall, floor, rear of cab, and inside the doors.

Re: '72 GMC K25 build 454/4L80e
 

pics

Re: '72 GMC K25 build 454/4L80e
 

It was time to install the headliner. Since this truck is a Sierra and not a Sierra Grande, it did not originally come with a headliner or the holes for the headliner trim. I decided to glue it to the roof using liquid nails. I used some cut 2x4's to brace it up overnight.

Re: '72 GMC K25 build 454/4L80e
 

It was time to install the new dash wiring harness. Every harness on the truck was replaced with a new M&H harness and I highly recommend them. The heater box was media blasted and painted a satin black. I got lucky and scored an NOS heater control unit, as well as an NOS ignition switch and most of the other dash switches. The dash and gauges assembly is all new. The tilt column is originally out of a '72 Cheyenne. I sent it out and had it completely rebuilt/restored.
I also mocked up installing the TCI transmission controller in the center console.

Re: '72 GMC K25 build 454/4L80e
 

pics

Re: '72 GMC K25 build 454/4L80e
 

The dealer installed underdash A/C unit was completely disassembled and restored by a friend of mine to as new condition. I had the original A/C bezels re-chromed and reinstalled the unit. It looks great.
After the underdash A/C was installed, I installed the glove box and glove box door.
I set the factory bucket seats in place to get an idea of how they would look.

Re: '72 GMC K25 build 454/4L80e
 

Due to the longer 4L80e trans, the transfer case is 3" further to the rear than stock...combine that with the 2" body lift, and you get a transfer case shifter that is too low and has a much longer throw than stock. I had to modify the stock trans hump; first by elongating the cover to allow for the longer shifter throw, then making a cardboard template, then cutting the some sheet aluminum and riveting it to the cover. Next I fabbed up a steel trim plate that will screw through the carpet...I had it chromed...it looks pretty good.

Re: '72 GMC K25 build 454/4L80e
 

pics

Re: '72 GMC K25 build 454/4L80e
 

Looks great! Are you going to put rubber under the plate from both sides,
To help close the gap.

Spike:smoke: