1978 Chevy K20 longbed with nearly 500,000 miles! LS Swap begins!

[Nick_R_23]

This is my 1978 Chevy K20 longbed!



Oh wait, this is better My dad bought this truck nearly new, way back in the early 80's. It's been in the family quite a bit longer than I've been alive, and I remember riding around everywhere in this thing. I've added the upper light bar and tube bumper, but aside from that, it's been mostly unchanged for as long as I can remember it. One day, I would like to completely restore the truck, and I'd like to take it back to that look as much as I can, but for now I'm focusing on getting it back on the road! The odometer has rolled over multiple times, and I believe it is sitting at somewhere close to 467,000 miles.



The truck is currently outfitted with it's (pretty sure original!) 350 engine, although I know the heads have been replaced multiple times before due to the valves receding into the heads from soft seats. The transmission is an SM465, with an NP205 transfer case, a Dana 44HD front and 14 bolt Camper Special rear axle and springs. The front has an Add-A-Leaf kit and there is also a 3" body lift. 33x12.50x16.5 tires and 16.5x10 American Racing Outlaw II's.

Here she is this winter hanging out with the local riffraff.



I had briefly (and regrettably) sold this truck several years back due to buying a house and needing to majorly downsize the vehicle population. It stayed local for a year or two, but after that I lost track of it. Just last year, a friend texted me and told me he had seen a truck listed on Facebook that looked like mine, and sent me the link. Turns out it was, and was only a few miles up the road! I took the rest of the day off work on the spot, and went to go rescue the old girl. Sometime while it was away, the clutch went out and the guy took it to a "mechanic" to have the clutch replaced. I'm not sure how you can screw a clutch job up this bad, but the story is whatever the guy did, the engine overheated badly immediately afterwards, and it was parked since. The carb, intake, distributor, and valve covers were missing, and knowing the mileage on the engine, I decided to finally let it retire - she's done pretty well! All said and done, I bought her back for $500 and towed it home right then!

Fast forward to today, after sitting for another year, it's time to bring her inside to get started with some long awaited and well deserved upgrades!





I always thought this truck was the biggest truck out there as a kid, so it took me a little by surprise when it cleared my garage door no problem



And a little preview of what's to come!

[TrailerTrash]

Awesome story I love reading threads like this.

In for more man keep it up

[Nick_R_23]

Thank you!

This is as far as I was able to get this weekend. Started stripping the old engine down to get it ready to pull.



This is incredibly clean for the mileage this engine has!



Got the exhaust, starter, and alternator all pulled. Someone installed this exhaust in the time it was away. Whoever thought it would be a good idea to make the turn downs point straight at the gas tanks was



I’m just noting this so I remember to fix it in the future. I don’t think you’re supposed to be able to do this!

[400/400]

Cool truck and story! I’m partial to K20’s myself.

I’ll follow along.

[LT7A]

I'm happy for you. It will be cool to see it brought back to a running, driving, working truck.

[Nick_R_23]

Thank you guys.

I starting buying some of the fuel system parts that I’ll be needing. I’ll also be buying something else for another LS swap project, but will have some parts that I’ll be using for this one. This is definitely going to be an expensive weekend!

To start off with, I decided to keep the dual tanks and make the system as simple as possible. I ordered up a pair of Holley C/K fuel pump modules with internal regulators and Hydramats.



I already know exactly what will happen, so I’m being smart this go around and getting all new tank straps beforehand!

[Nick_R_23]

I ended up picking up a 2012 5.3L LC9 engine (all aluminum) with 120,000 miles for my Exocet project today, for only $1400! While this engine doesn't have much to do with the truck itself, it will be donating it's truck-style intake for this build, as the Exocet will require an LS6 intake. This intake will match the returnless Holley fuel pumps, and also uses the newer 4 bolt throttle body, which will get converted over to a 90mm cable throttle body. No pictures yet, but I'll be picking it up next Friday!

I did do a bit more junkyard hunting, and I think I came across the right gauge cluster to rob the water temp gauge from. I couldn't read the VIN number or the door tag, but it did have the hood with the bump on the front, as well as the fuel gauge reading "Unleaded Fuel Only", so I'm pretty confident I got a 79-80 cluster.



Two brand new stock replacement 1978 Precision fuel tanks came in from Oreilly's today as well.



When I purchased the Exocet's 5.3L, I got them to throw a stock airbox assembly in with the deal. I'm not 100% sure it will work yet, but my vague plan is to move the battery over to the driver's side, and use the stock air box where it would normally go on a modern truck.



Here's a high quality mock-up for everyone

[Nick_R_23]

I also ordered a full set of filler necks and hoses from LMC Truck.

[Nick_R_23]

The Holley goodies arrived!

[Nick_R_23]

So this all aluminum 5.3 came home today! While this engine itself is going into my Exocet project, it will be donating its intake manifold for this project.

[Nick_R_23]

I picked up a few more pieces today at the junkyard. I got a full hydraulic pedal assembly, master/slave cylinders (for test fitting), and a hydraulic bellhousing for the SM465.





After a little bit of elbow grease





Confirming that the new LS flywheel and clutch assembly does in fact clear!

[Warrens69GMC]

Not to derail you, but have you considered using 1987 gas tanks that are baffled for EFI?

[Nick_R_23]

Originally Posted by Warrens69GMC

Not to derail you, but have you considered using 1987 gas tanks that are baffled for EFI?

Yes, but the Holley units aren’t compatible with the baffled tanks and I didn’t want to deal with mismatched tank filler hose sizes (I ordered the complete OEM filler and hose assemblies). I’ve been very happy with the Hydramat setups before.

[Warrens69GMC]

ok

[Nick_R_23]

Slight change of pace on the clutch and bellhousing setup. The original plan was to run the hydraulic bellhousing with an external slave cylinder. After picking one up to test fit, it turns out that the 2010 Camaro manifolds dump exactly where the slave cylinder is! So now, I will be running the original SM465 bellhousing, and going with an internal slave cylinder setup.

On to better news, more parts are showing up! I received my filler necks, gas caps, and hoses from LMC.



I also picked up some EFI fuel hose, but will likely have to get more as I wasn't sure what size I needed. Also got some 5/16 to 3/8 adapters just in case.



And finally, the harness and tank switching valve for running EFI and dual tanks. This is from Harnessworx/gmachinz and is incredible quality!

[Nick_R_23]

Last night was another ordering spree! I bought a RAM internal slave cylinder with remote bleeder, 36” -3AN braided line to run to the master cylinder, a Earl’s 3AN to 12mmx1.0 ISO adapter fitting for the master cylinder, a gasket and seal kit for both the SM465 and NP205, since it looks like both are covered in oil and grease. This morning I will also be ordering a clutch fork boot and tank pads from LMC!

I had a bit of free time last night, so I assembled the fuel tanks.

Prepping the Holley 12-308 units and installing the Hydramat.



Being gentle, it’s her first time!



Perfect fit! New O-rings and locking ring installed.



Both tanks completed!

[Nick_R_23]

Alright, finally made some progress on the truck itself!

Started off today by removing the driveshafts. The rear U-Joint was so worn that there were no needles left. I'm surprised it didn't fall out of the yoke! Definitely had it's moneys worth used up!





Drained the transfer case and transmission. The fluid came out looking brand new on both, so a gasket and seal kit should be good to get both cleaned up and back in service again.



The transfer case is out.



Transmission came next!



These SM465's sure are incredibly heavy for their size. That's cast iron for you!



And finally, the engine came out last!





I did a quick wipe down of the engine bay. Picking up some new engine and transmission mounts in the morning, and a few other small parts. The next step will be a lot of cleaning! I've already scraped a 5 gallon bucket's worth of grease off everything so far.

[Nick_R_23]

I picked up a new pair of motor mounts, upper and lower transmission mounts, heater motor resistor, and a new bolt and washers that were missing from the transmission mount. Napa sold me one automatic mount on accident, but quickly swapped it out for the correct one.



As a nice bonus to end the weekend, I sold the ENTIRE engine setup from the truck. The short block, alternator, power steering pump, pulleys, belts, starter, fuel pump, manifolds, and even the whole exhaust system sold in one go for $400! Sure was nice to get a little money back and not have to kick that around the shop.

[Nick_R_23]

Started off this weekend by finishing up a bit of cleaning and removing the old engine mounts.



I spotted a crack in the front crossmember, grooved the area and drilled the end to prepare to weld it.



Welded and painted.



New motor mounts installed!

[Nick_R_23]

A few more parts trickled in today. I was hoping for at least the transmission and transfer case gasket kit, but I guess I’ll see them next week. The Ram throw out bearing, the Earl’s adapter, and the 36” braided line.



Since not all the parts showed up, I got onto the cleaning and painting. The crossmember got a nice bath and fresh coat of paint!



The transmission was caked and took me most of the day and a nearly full case of brake clean to get it to where it’s recognizable as a transmission again. Mostly there!



Fully cleaned and ready for paint.



Shiny! It’ll still be resealed when the gasket and seal kits come in, but shouldn’t need much, if any, touch up when that happens.

[Nick_R_23]

Kind of a side step. A while back, this was the original plan for the truck - a carb swap, just to get it running and driving, and back on the road.



I also lost some pictures in between showing me picking up and cleaning up the 2003 Tahoe 5.3L for this build, but here it is on the far left - replaced the oil pan gasket, front and rear main seals, front and rear cover gaskets, valve cover gaskets, ceramic coated Camaro LS3 exhaust manifolds, and Dirty Dingo slider mounts, and new plugs and wires.

[Nick_R_23]

I picked up a new radiator and hoses locally, using stock 99-02 Silverado hoses. These have worked perfectly with a stock 73-87 radiator in my '86 C10 swap before.



A new pair of Magnaflow stainless mufflers came in today!



Holley's Hooker exhaust kit showed up also! Yes, I had to mock it up inside!



A brand new 2 piece fan shroud and hardware came in from LMC Truck to top everything off!

[focusedontheprize]

Christmas in June, always great when new parts show up.

[Nick_R_23]

Unfortunately I have to pay for this Christmas...

This turned out to be a really busy weekend, I got quite a bit done on the truck!

A few more parts showed up. New pedal pads, pedal bushings, SM465 and NP205 gasket and seal kit, clutch fork boot, and tank pads!



New driver side battery tray, clamp, and mounting hardware, reverse switch for the transmission, a box of 1/4" rivets for the fuel tank straps, and a new input bearing retainer.



Billet valley plate, new valley gasket, exhaust manifold flanges, and new gaskets.



I started to installed the new bearing retainer on the transmission. I noticed the bolts originally had aluminum washers, which are one time use, but the bolt surface is a rough cast iron finish. I picked up some bonded washers to help with sealing that area a little bit better.



New bearing retainer installed!



I had to epoxy the magnet back into place, the glue had finally released after all these years.



Pretty damn clean on the inside!



Shift forks are in good shape as well.



All of the gaskets have been replaced, touched up the paint and also painted the bearing retainer to match.



Installed the reverse switch.



Assembled the throwout bearing and lines, test fitting how it will go together.



The new fork boot is installed.



Picked up some new bellhousing bolts and washers.



The bellhousing is installed and the transmission is finished!

[Nick_R_23]

I picked up a few tools for setting the throwout bearing depth and a helicoil kit for the transmission adapter.



The ball stud had to be machined down as it just barely interfered with the lines.





I didn't take any pictures, but the bearing depth is set with a .130" gap. RAM called for .150" to .200" gap, but I later found the .200" gap is recommended for twin disc clutches. Most factory specs are .100" to .125", and the included shims would either put me at .130" or .190", so I settled for the .130".





The engine and transmission mated up perfectly!



There is excellent clearance all the way around. Air gap setting looks to be spot on.



Next up was starting on the transmission adapter. Drilled and helicoiled the stripped hole.



It was also painted to match!