1972 GMC Farm Find LS Swap

['68 C10]

Did lots of work to the deck surface and getting the threads ready for the bolts. Decided to go with studs over TTY bolts or even ARP bolts, just for reusability (I know ARP bolts can be reused) and more so if I ever decide to add a power adder down the road. Also, went ahead and dropped the pan down to install the Melling oil pump (the green O-Ring is a pain!) and the LS2 timing chain.
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['68 C10]

Finally got the top end installed and torqued. Cleaned up the front accessory drive as well. Motor fired up almost immediately. Oil pressure climbed to almost max on the gauge, so that's a plus for various reasons for the motor's sake and for mine knowing the o-ring is seated properly on the pump. I’ll get a video of it once I get the front end on and radiator plumbed.

[1971Stepside]

Installing the cam, springs, etc. on mine this Monday. Now I'm worried...I've pulled my valve covers and it is clean so hopefully all is good.

Nice build, I'm watching your progress.

['68 C10]

I doubt you have anything to worry about. Despite the rust, my motor did actually fire up and run, so I wasn't worried about the bottom end much. The top end did need work. I found two of the plugs coated in white on the tip and one plug looked brand new so I know there were some issues. Now all is well though.

['68 C10]

Started off the day by thoroughly cleaning out my garage. I don’t have a pic of the madness, but just let me say that it’s crazy how many boxes and parts you can amass throughout the course of a project.

As far as progress goes, I got to work on getting the radiator in it’s new home. I was initially going to use a stock 99-07 truck radiator with LS1 fans, but decided to go the Champion route with the Fans already installed. I’ll just have to modify the electrical connections on the end of the Champion fans to mate to the Nelson Performance Fan harness. I needed up modifying the factory mounts by shortening them. The radiator is about 2 inches less wide than the factory radiator but it still fits on the factory lower supports.
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['68 C10]

In order to route my exhaust through the Porterbuilt crossmember ports, I discovered I’d have to change trans crossmembers as the CPP one sits right in the middle of where the exhaust would be routed to tuck up in the frame. The solution was to order a Dirty Dingo Trans crossmember. The humps will provide enough exhaust clearance and still have space between the member and the cab floor. Took some fiddling with the parking brake cables to mount it. I ended up installing it with the cables above it. I’m sure it’ll rub over time if the brake gets utilized often, but I hardly use mine. Fit and finish of the member is great, I’d recommend it to anyone.

['68 C10]

Worked on the battery tray as the day of putting the front end back on grows closer and closer. I cut of a couple of portions, including the AC brackets, the lipped portion on the side, and the extra metal around the top that wasn’t needed. I then added a piece of angled metal to the upper portion in order to mount it to a factory bolt on the upper driver side. Then just drilled the side holes into the bracket and into the core support. Came out better than expected, and also didn’t have to relocate the horn.

Front end goes on tomorrow, then it’s plumb the cooling system and mount the overflow tank. Driving is near!!!
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[boynton]

Nice work on the battery tray. I also really like that dirt dingo trans mount. I have the cpp on my truck but that would have probably helped me a bit!

[c104life]

What was the part # of the champion radiator you ordered for your truck

['68 C10]

CC162 if I remember correctly.
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['68 C10]

Got the front clip back on. Looks like I’m going to end up doing drop shackles and lowering spindles as well, doesn’t quite sit as low as I would’ve liked.
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['68 C10]

Started the task on plumbing the cooling hoses etc to the radiator. After several trips to the parts stores I’ve got a makeshift set up until I can get a better reservoir, as the one I intended on using had a small leaking crack. Ultimately it’s fine because I wanted to use a different reservoir other than the bulky factory NBS truck one. So for now, I have hoses straight from the firewall to the water pump w/o the “T” in line. In turn I routed the steam hose from the TB to the 1/4” nipple below the cap.

Filled the system and heard the familiar sound of liquid hitting the ground.....and a lot of liquid. After fretting on it possibly being the head gaskets, I discovered the coolant crossover plates had no seals or orings. Quick trip again to the store alleviated the leaking fluids. Got the intake back on and all the hoses connected again.

Now on to wiring the fans and we will be ready for the drive!
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['68 C10]

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['68 C10]

Got the fans wired. I have a Nelson Performance harness that I’ll be using in the future but for now I just wired them to an unused ignition spot on the factory fuse block.
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['68 C10]

Ran into a debacle the last few days.

I took the truck out for it’s initial shakedown run and when I returned I couldn’t help but notice #4 cylinder didn’t have the same color on the primariy as the other 7. It still looked new, and definitely not the “bronzed” coloring that stainless turns when it’s been heat cycled. This started the troubleshooting.

Swapped coils - no change
Swapped plug wires - no change
Spark test - spark confirmed

I ended up doing a compression check on cylinders #2 and #4 for comparison......

#2 - 160psi
#4 - 165psi

So now I can breathe easy knowing it’s either spark or fuel.
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['68 C10]

Digging deeper into the non-fire in #4 cylinder, I turned to some technical data. The first pic is from my SuperChips Cortex that I’ve had for years in end. Had it initially for my G8, before HPTunders offered support for them they were the thing to have, but have it now just for an OBD2 code reader and datogger. These were the shots on the Short/Long term fuel trims at idle-1500 along with the O2 sensor readings.

Bank 2 readings were off on both as you can see. The O2 sensor is brand new so that led me to believe it was a fuel issue.
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['68 C10]

Seeing how I don’t really have a feasible way to test the injectors, I have a spare set of injectors, so I swapped in a replacement into #4 port. Initial start up was leaps and bounds better. These are the readings, after noticing there was finally heat on the #4 primary tube. Issue solved!
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['68 C10]

Also went to work on the temp adapter and getting the factory gauge to read. I broke the brass adapter I intended to use on the passenger side, so I just decided to go with the three wire FBody sensor in the factory location and tap that into the factory gauge. I know it won’t read in the middle of the gauge but all I need to do is document the temp through the PCM in reference to the gauge location and monitor any increases on the gauge. Install was really straightforward on this. When hot it reads about 1/16” above the cross-hatched portion on the gauge. I didn’t get a good pic of the gauge when it was hot, but did during cool down to show it at least was referencing a temp to the gauge. If I want to I could put a resistor in and move the needle towards the middle, but that’s a big IF.