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The year was 1987. Having already owned a couple of Blazers, I sat down and drew up a list of things that I wanted to have in the next one that I would buy. I had already owned a CJ7 for a while and really liked being able to take the whole top off. The CJ was very capable, but was just too small for my liking. I had owned a '72 Blazer for a short while and then had a '77 Blazer for several years, so I knew that the later models had more creature comforts and didn't squeak and rattle quite as badly as the '69-'72 Blazers. (Though the First Gen Blazers have more character!) So part one of the plan was to find a '73-'75 model year K5. It would have the newer body style yet still have the fully removable hard top. After searching for some time, I finally ran across a suitable candidate. It was a 1975 GMC Jimmy, the last model year for the fully removable hard top. The body was solid, it ran well and the transmission had no reverse, thus the price was right. Perfect! My plan was to swap out the Turbo 350 for a Turbo 400 anyway, so why worry about the tranny? That just made the price more attractive! The rig had been used (and neglected) by a retired guy that went fishing in the mountains in it. Here's what it looked like when I got it:
A real snoozer, eh? Can you dig those wide
whitewalls? Next
came the drive train. I'd blown out 3 12-bolt rear ends in my previous K5,
the '77. (You can see more about it here.)
So I knew that something much beefier was in order. I first thought about
a Dana 60 8-lug out back and a Dana 44 8-lug up front. A fellow at a
junkyard questioned why I would want to mess with trying to install a Dana 60
out back, when a GM Corporate 14-bolt would bolt right in and be much
stronger. So the search began, and soon a 1974 GMC K-25 gave up its axles,
complete with 4.10 gears. Excellent! (Looking back now, I wish I had
grabbed a Dana 60 front axle before the prices went sky high.)
Next came the rest of the drivetrain. I located a Turbo 400 with an NP205 attached, from a 1980 1-ton GMC. I got the crossmember, shifter, etc with it. They even threw in the driveshafts. The front shaft bolted right up after the trans and transfer case swap. I had the monster 1-ton rear shaft shortened to fit as well. For
the engine, I didn't want to go too wild, since at the time this
truck was to be my daily driver. I toyed with the idea of dropping in a
454, but single-digit fuel mileage wasn't too appealing! I had read a bit
about the Tuned Port Injection engines that were going into the Corvettes and
thought that would make for an interesting transplant. But remember, this
was back in 1987, when swapping a fuel injected engine into an older vehicle wasn't exactly
popular. Most motorheads were still quite wary of the new fangled computer
controlled EFI engines. But
having a degree in Computer Engineering, I figured I could make it work. Then, by a stroke of luck, in 1988 I spotted an ad for a complete TPI 350 that had come from a 1987 Corvette that was totaled, with just 7,800 miles on the clock. Hmmm, the price seemed right, so I went to take a look. I ended up getting the engine, complete with all the accessories still bolted to it, with the complete engine wiring harness and computer. I also got the 700R4 automatic, figuring I would use it for something someday. (It's an ornament in my garage to this day.) So
I took both over to the garage/barn that belongs to my friend, The Mad
Weldor. The place is affectionately known by all as
The Fantasy Factory. The Mad Weldor can build anything out of
metal. He's a master fabricator, so he
had lots of people stopping by all the time with hot rods, 4WD's and even farm implements for
him to fix or improve. He even has a small forklift that he used to lift
the engine and tranny up to the loft of his shop, where it would sit while I figured out
just how to install it and make it work.
Anyway, now that I had the engine, I had to determine how to actually install the thing! So I ordered up a set of 1987 Corvette factory service manuals and started reading. I learned what all the various sensors did, how they worked and why they were there. I also studied the wiring diagrams to figure out just how everything connected and interacted. Hmmm, looks like this isn't going to be too tough after all. Finally the day came to start the swap. So that I could still get around, I had picked up a '79 Dodge Aspen for $100, to drive while the K5 was down for the engine swap. (There's a whole 'nother story behind how I got the Aspen so cheap. You can read it here if you want). A
few buddies and I met early one morning at The Fantasy Factory and got out the
wrenches. One buddy, Dana May, a serious Ford bigot,
If only the rest of the swap would have gone that quickly... First, did
I mention that The Mad Weldor lived nearly 2 hours away from me, so I could
only go work on the truck on the weekends? Every Saturday, we would push my
beast into his shop, I would work on it all weekend, then we would push it back out on
Sunday evening, so he could use his shop for other work during the week.
(We're talking about a true friend here!)
I stripped out the wiring that I didn't need from the Corvette harness, then
wired in a 2nd fuse panel just for the extra circuits that weren't required when
my K5 was built back in 1975. Next came the new plumbing for the fuel system. TPI systems pressurize the fuel line from the tank to the fuel rail on the engine at 42-45 psi. There is also an excess fuel return line that bleeds off excess pressure at the regulator to send back to the tank. This meant that I had to re-plumb the entire fuel system to deal with the pressure, as well as to add the return line. I also had to drop the gas tank, remove the sending unit assembly, and install a fuel return line. Again, The Mad Weldor came to the rescue, TIG welding a fitting into the top of the sending unit assembly (well away from the gas tank!) An external Bosch fuel pump, from a V-12 Jaguar application, was mounted inside the frame rail, near the gas tank. Steel fuel lines were routed to and from the engine. Finding fittings to switch between the SAE parts of the truck and the Metric parts of the Corvette fuel system was not an easy task. But I scrounged up what was needed and moved forward. I used the factory mini headers that came on the Corvette engine. But
when I went to bolt them in place, the drivers side header hit the bracket that
the motor mount sits on. Once again, it was The Mad Weldor to the
rescue! (Are you seeing a pattern here?)
And here are a couple of shots after installation:
Over the years, I've added a Detroit Locker in the rear, seats from an '84 Mustang SVO and an Alpine stereo system. The rear also sports disc brakes, using brackets from TSM Manufacturing and calipers from a 1976 Cadillac Eldorado, complete with parking brake mechanisms. Here's a pic of the rig sitting outside The Fantasy Factory:
The wheels in the picture above are aluminum slotted mags from American
Racing Wheels, in size 9.75x16.5 inches. They're covered with BF Goodrich 35x12.50x16.5
Mud-Terrain
T/A's. Since the 16.5-inch wheels don't have
safety beads (as I found out after I had bought and installed everything), the tires come off the
beads quite easily if aired down
too low. To resolve this, the next set of wheels will be either 15 or 16 inch, with the 8-lug bolt pattern. Wheels of both these sizes have
safety beads that help hold the tire on at the low pressures often used off road.
Update: The wheels have now been replaced with a set of 15x10
Cragar Nomad
II chromed steel wagon wheels. They have a backspacing of 4.25 inches,
which did indeed require some grinding of the calipers and backing plates to
clear the front brakes. You can buy wheels with less back spacing and
avoid the grinding. But you will pay extra for the custom backspacing and
the tires get moved further out of the fender wells. For now the tires are
a set of 35x12.50/15 BFG Mud-Terrains that I had in the garage anyway.
When these are worn out, I'd like to try a set of 37-inch Goodyear
MT/R's.
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There's switched power to the ECM, power to the fuel pump, 2 circuits for the
injectors, (and I added a fused power supply to feed the kickdown circuit on the
Turbo 400 tranny). While The Mad Weldor is a genius when it comes to mechanical stuff,
electronics and wiring weren't his bag. He walked over several times as I
kept adding to the pile of "unneeded" wires from the Corvette harness,
just to ask if I was really sure that I didn't need all that stuff!
