78 K20 modernization project
 

I am starting with a bare bones 71,000 mile 78 K20 Scottsdale camper special and plan on upgrading the creature comforts and the technology as well as fixing the body damage left over from the previous owner.

I already yanked the engine to do a mandatory clutch job so while I had the engine out I cleaned it up, installed a little bigger cam & lifters with matching valve springs and silicone valve stem seals, double roller timing set, all new gaskets, a Performer RPM intake, an Edelbrock 1406 carb and headers. When it went back in it got the new clutch and a rollerized pilot bushing along with the resurfaced flywheel.

Valve covers are an 85-86 vintage TPI Camaro part and come from the factory with studs and wide force spreader hold downs. They came stock a dull silver color so I painted them, the oil fill cap, breather and the air cleaner lid satin black so it all matched.

Re: 78 K20 modernization project
 

Along the way during the clutch job I found the worst looking cap & rotor that I have ever seen on a running vehicle.

http://67-72chevytrucks.com/vboard/s...d.php?t=362601

Replaced those with an MSD cap & rotor kit and a spare stock coil I had on the shelf. Still need to find the new MSD plug wires I have in a box somewhere.

Re: 78 K20 modernization project
 

The driver side all plastic window crank handle kept popping off the mounting stud so I decided to retrofit a set of late 60's & early 70's metal window crank handles.

http://67-72chevytrucks.com/vboard/s...d.php?t=359291

Not quite a bolt on deal but a quick hit of the die grinder fixed that.

They look like they belong on the truck.

Re: 78 K20 modernization project
 

While I was doing the window crank handle job I decided I needed something better than the plain old cheap radio and single center dash speaker for tunes.

http://67-72chevytrucks.com/vboard/s...d.php?t=359332

I started with the door speaker install using some speakers I had on the shelf for another project.

Re: 78 K20 modernization project
 

I installed an old post type cassette player from another car I had but it ended up having a dead digital display so I ended up cutting the dash to install a fully function modern CD player.

After that I built some cab corner speaker enclosures to house the 6x9's that matched the door speakers I robbed from another project.

http://67-72chevytrucks.com/vboard/s...d.php?t=359330

I still need to finish the edge filler pieces and seal the housings to the cab corners but it sounds great all ready so I have been putting it off for other more important projects.

Re: 78 K20 modernization project
 

I ended up giving the Edelbrock 1406 carb back to my brother after he changed his mind about the trade I had made for it a while back so in order to keep the truck on the road I robbed the 750 Demon carburetor off my 68 Camaro that is not back on the road yet after a complete drivetrain rebuild and upgrade.

I had to cut a section out of the heat shield to clear the Demon fuel line but I haven't taken a pic of the Demon carb on there with the modified heat shield.

The stock Q-Jet worked fine on the stock engine but the air & fuel mixture screws did not make any changes when turned so it could not go back on the truck. The best I could get out of it was 6 inches of vacuum. With the 1406 I was able to get 14 inches of vacuum out of it. Not bad for the size of the cam in there. Isky 280 degree .480" lift hydraulic.

Re: 78 K20 modernization project
 

I scored a set of power window / power door lock doors at the local pull-it-yourself wrecking yard today along with a set of matching stainless sport mirrors and a better driver side door gasket to replace my pinched and dysfunctional one.

The passenger door was from an 87 Suburban and the driver side was from a 77 Truck so I have the correct two button driver side window switch. The driver door is a little rough but it is complete with all the PW / PDL parts I need to upgrade my driver door. My door needs a little attention to the leading edge but not too much. The work on it will be far less than that of cleaning up the donor driver door.

I also got a set of 5.7 liter TBI fuel injectors, a 1227747 ECM from a 5.7 TBI truck with the T-400 transmission along with the crossover wiring from both donor vehicles for the power window system and a better transfer case shifter boot.

It was too dark to take any pics of the new parts when I got home but I will add some tomorrow.

Re: 78 K20 modernization project
 

Future plans for the truck include a conversion from the SM465 manual transmission to a 4L80E transmission and to install the nearly completed TBI 350 I have in the shed along with with it.

The TBI 350 has been rebuilt and converted to hydraulic roller with the parts scavenged from a Vortec truck. It should wake up the TBI motor tremendously. I just have a few more pieces to purchase before I can finish assembling the engine.

My knees are shot so the heavy clutch is painful to use and when paired with the 5.13 gears the truck has it makes for some very frequent clutch usage.

The original owner swapped in 5.13 gears so towing his fifth wheel was a little easier with the mighty 170 hp 350.

I may put a T-400 into the truck to get it converted to an automatic before I do the 4L80E conversion. I have the 4L80E but I need to find a good donor vehicle with the NP205 and a T-400 to be able to make the conversion to the 4L80E. I can run another type of transfer case that is more common and do the T-400 conversion any time I have the time to tear it apart.

Once the TBI engine goes into the K20 I will transplant the current 350 into my old basket case of a 67 C-10 truck to give it some new life and begin its transformation into a 1970 era looking version of the modern sport trucks.

The C-10 will get C3 Vette disc at all four corners with PBR aluminum calipers, quick ratio steering, big sway bars and a whole host of spare parts I have from my 68 Camaro. It will also get converted from a long bed truck to a short bed clone and be converted from six lug to five lug. The rear wheel wells will get widened out to the full width of the frame clearance so the largest rear tires possible can be tucked in the wells.

Re: 78 K20 modernization project
 

Scored a set of front bumper guards to dress it up a little. They make a nice improvement to the looks.

Re: 78 K20 modernization project
 

Had to lose the bent up rusty painted step bumper so I snagged the 80's vintage sport bumper off my 67 C-10 and put it on.

Painted the hitch while I was in there and flipped the ball to the other side on the stinger to match the height of the truck.

Still need to find or fabricate some inner brackets and get some more carriage bolts.

Re: 78 K20 modernization project
 

The original owner "repaired" the dysfunctional washer pump by installing a race car style push button momentary starter switch in the dash next to the wiper switch and connecting it to an external washer pump.

Didn't work when I got the truck so I swapped in a washer jar from an 89 new body style truck with the integral washer pump.

Simple hook up with two wires going to the original on wiper motor washer pump. Yellow wire from wiper motor goes to the pink wire on the donor truck washer pump. The other wire is the ground and they are connected together.

Turns out my dash switch works fine and the external pump the original owner installed was defective.

Works great and holds about a gallon of washer fluid.

Re: 78 K20 modernization project
 

Nice truck. I really like the 3/4 ton 4x4's. What's that mounted on the back of the bed near the passenger tail light?

Re: 78 K20 modernization project
 

Nicely put together build. I have read most of those when you did them but I never read here. The most recent, is something I will be doing to mine too. Looks "right" in there. Good job. :thumbs:

Re: 78 K20 modernization project
 

Thanks, those are low profile tie down points back by the tail lights.

Re: 78 K20 modernization project
 

Thanks, it is a slow process due to the complete lack of funds and no garage to work in but it is making some progress anyway.

The next part of that install is to see if I can get the newer wiper arms with the arm mounted spray nozzles to fit under the cowl and plumb them up for better washer performance. It will let me clean up the original owners mickey mouse washer hose routing job too.

When I do the auto trans conversion I will install the newer column I have that has control stalk delay wiper controls. Two speed wipers with no delay suck.

Don't know if I need to install the wiper motor from the delay wiper donor but I have that too if needed.

Re: 78 K20 modernization project
 

Thats a really nice looking truck. Great job on it so far.

Re: 78 K20 modernization project
 

Thanks. I can use all the motivation I can get to keep working on the truck.

Still a ton of stuff to do but I keep chipping away at the list.

Re: 78 K20 modernization project
 

68_TT, you are giving me motivation to work on mine even more

I think I have your truck's year younger cousin! 79K20

http://i450.photobucket.com/albums/q...g?t=1266764591

Re: 78 K20 modernization project
 

Nice progress! Your truck is looking good. The bumpers look great.

Re: 78 K20 modernization project
 

A bed with the gas doors is like yours is on my shopping list at the wrecking yard.

I scored a perfect driver side door this weekend so I now have both front fenders and both sport mirror power doors to go on the truck some time soon. Just need to remove the wrecking yard makings and color match them to the truck before I put them on. I don't want to paint the whole thing yet until I get the bed I want on there.

Re: 78 K20 modernization project
 

I scored big time this weekend courtesy of a C4C victim 87 K10 truck at the local pull it yourself wrecking yard.

I snagged both in-tank fuel pump / sending unit assemblies, the switching valve, all the wiring and fuel line plumbing as well as the 27-spline NP208 transfer case and the under dash ECM carrier. Saved me a ton of cash on the fuel system alone.

While I was there I also picked up a GM Goodwrench remanufactured 4L60E out of a 93 4x4 with the Vortec V6 so it also had the GM rated 2025 rpm stall converter in it which was also new with the reman trans. It has the early four-bolt tail housing so it bolted right to the NP208 without need for an adapter plate. New these were $1400 for the trans and ~$200 for the converter so nice score for $55. Don't know how old they are but the fluid was red and the pan was clean. I will have to check the converter to see if there is a manufacture date on it. I have used this torque converter in several other projects and it works great. With a strong small block it will stall to about 2200 to 2400 rpm which will be great for the cam that is in my 350.

I also grabbed the engine wire harness out of a red-blue connector PCM 93 C1500 so it will plug right into the 16197427 PCM I have for the project.

Out the door I spent less than $200 on everything.

My EFI and overdrive trans retrofit project are now much closer to happening. Now all that is left is to fabricate the Holley pattern to TBI adapter plate for my Performer RPM intake and get to work putting it all in the truck.

Once it is all in there I will have to figure out what to do with the driveshafts if I don't find a long bed 700-R4 / NP208 driveshaft donor before then. I would like to put completely different driveshafts in the 78 with the swap so I can keep the SM465 / NP205 setup complete as a package that can go back in easily or be sold as a package to somebody else who wants to go to a manual trans from an auto.

I have a nice one-piece aluminum driveshaft out of a C1500 that may go in there in place of the steel two-piece unit in the 78 now. I will have to take some measurements to see if it will work now that I have the new trans and transfer case. I'm pretty sure it will need to be shortened. No big deal.

Re: 78 K20 modernization project
 

Nice truck and really cool build man!

Re: 78 K20 modernization project
 

Wow, someone from the salvage yard better call the cops up there and let them know they got robbed. Nice job on the parts!

Re: 78 K20 modernization project
 

They have fixed prices for parts so every transmission is $55 no matter what it is and it comes with the converter.

All sending units are $9 no matter how rare they are but you have to buy the pumps separate.

The engine wire harness only cost $9 but took several hours to get out in one piece.

T-case with adapter housing was only $65 too.

An engine assembly with all the accessories is only $135.

I love that place.

Re: 78 K20 modernization project
 

Fine looking truck!!! Nice to see someone doing it right. Great pics of the distributor cap by the way. I'd say she was running a little bit hot that night.


Bone stock red on red '81 GMC K2500 longbed 350/sm465/corp 14bolt outback and dana 60 upfrt.

Re: 78 K20 modernization project
 

I had been mulling over my plans to change the 78 K20 to an overdrive automatic, installing a newer motor, converting it to EFI and upgrading it to power windows & locks and adding sport mirrors to it.

The truck has been so reliable and solid I had second thoughts about tearing it apart. I found a 74 K10 on CL for a reasonable amount of money that was missing the drive train.

I picked it up on Thursday and it came with an extra front clip and another set of axles & tires attached to the Blazer they were on because the kid didn't feel like taking them off of it to give me what was in the ad.

The 74 is a bare cab with nothing under the dash but it had factory A/C so it will be much easier to install than putting A/C into my heater only 78 K20. It also has the auto trans 4x4 tunnel so I won't have to fill that hole where the shifter goes through on the K20 and it has a sliding rear window the K20 also does not have.

The Blazer floors are really rusty and it has had some metal fatigue issues in the door jambs so I am just going to part it out and put the best stuff from the two onto the 74 K10 and scrap the rest of it. I thought about making it an off road beater with all the serviceable parts that come off of the other two trucks but don't feel like spending the money to make it safe to drive or put a drive train into it.

One of the clips that came with the new acquisition is a near perfect 70's vintage set that is painted exactly like my 78 K20 so that will be going onto the 78 to fix the damaged driver side fender and cancer infected passenger side fender. I may take the driver side door off of the Blazer to put onto the K20 if my attempt to straighten out the damaged edge on the current one doesn't turn out.

Pics of the clip swap on the 78 K20 to follow after I get the K10 and K5 merged into one and the carnage cleaned up.

Re: 78 K20 modernization project
 

i wish i was closer i'm in need of a cab lol my 73 is rotting like no tomorrow... po did some stuff to it that mother nature loved

Re: 78 K20 modernization project
 

The clutch fork broke so I ended up yanking the whole drive train, resealing the leaky transfer case and the transmission adapter, and upgrading the engine to a high volume pump and installing new rod & main bearings.

http://67-72chevytrucks.com/vboard/s...t=clutch+broke

Re: 78 K20 modernization project
 

The day after I got the whole drive train back into the truck, got it assembled and back onto the road the ignition mechanism failed.

http://67-72chevytrucks.com/vboard/s...=1#post4004633

It seemed quite coincidental to have something break right after I did all that work but nothing I did was even close to the failed part so it was purely bad luck. At least it failed in the morning when I was going it warm it up prior to heading off to work instead of failing at work and stranding me with a broke truck and no tools or parts to fix it with.

It is now back on the road and runs & drives better than it has since I owned it. It shifts smoothly into all gears with little to no effort and the clutch works with minimal pedal movement instead of having to push the pedal to the floor all the way to be able to shift as before. It is much nicer to drive now but the clutch still kills my knee to use it.

Now I can get back on the 67 C-10 to K10 conversion project after a couple week delay fixing the K20.

Re: 78 K20 modernization project
 

Scored a great retrofit shifter boot for the NP205 shifter out of a wrecked Saturn with a manual trans that fits the NP205 boot retainer ring perfectly.

http://67-72chevytrucks.com/vboard/s...77#post4209677

Looks great, won't let in any noise, fumes or moisture like the damaged old one did.

Plenty of height for full range of motion with no binding.

The price was right too at only $3.

Re: 78 K20 modernization project
 

Scored a delay wiper switch & delay module with pigtail at the wrecking yard today.

Just have to dig in and see how the wiring is different between the delay module connector and the non-delay switch.

http://67-72chevytrucks.com/vboard/s...45#post4209745

Hopefully it won't take any funny business wiring wise to make them work.

Delay wipers are a tough thing to live without after you have had them for so long. Not having them is the worst thing about driving the K20 in bad weather.

Scored a tach cluster small fuel gauge too from the same truck the delay wipers parts came out of. Unfortunately the tach was gone and the hack that took it busted the housing & damaged the circuit board getting the tach out.

Just have to make a new overlay for the Camaro tach now that uses the 80 psi oil pressure gauge to match my engine so I can complete the tach cluster I am building and change it out on the truck.

Re: 78 K20 modernization project
 

I put the delay switch in and it has a mind of its own so either the switch or delay module or both have issues unless there is something different with the wiring.

I couldn't find where I stashed the other two switches I have to test them too so I will have to dig into this again at a later date.

Anybody have a wiring diagram that shows the delay module wiring? I have one with the standard 2-speed motor only.

Re: 78 K20 modernization project
 

Since I had the dash panel off to access the wiper switch I took the opportunity to replace all the general lighting bulbs with 168 bulbs and checked to make sure they all worked while I had it apart.

I am going to retrofit the truck with TBI so I needed to install a newer speedo with the optical VSS capabilities into the stock housing. Amazingly the 78 housing had a hole pretty close to the right size for the optical sensor to go through. All I had to do was enlarge it a little to make room to get the plug through and create clearance for it to sit right with the speedo in place.

Used a hacksaw blade to open the existing hole up just enough to clear.

I also reset the mileage on the optical VSS speedo to match the K20 to within a 1/10th of a mile before I put it in.

Road tested and both the speedo and mileage counter work correctly.

Re: 78 K20 modernization project
 

I also replace the 60 psi oil pressure gauge with an 80 psi gauge from a diesel square body since after I installed new rod & main bearings and a high volume oil pump I have more than 60 psi oil pressure so the stock gauge is pegged 99% of the time.

I didn't like the mismatched gauge fonts & band colors so I swapped out the rest of the gauges for newer ones to match the oil pressure gauge & VSS speedo. I used a diesel water temp gauge that only goes up to 240 degrees too since I always hated the C-H temp gauges. How hot is H? Fixed a problem with the temp gauge too while I was at it. One of the clips came half way out of the housing and made the temp gauge only work part of the time. I was able to snap it back into the housing securely and the new gauge works properly now.

I repainted all the gauge needles with Chevy orange since I had some on hand. I've used it in the past and it works very well against the black gauge faces. In bright light it changes to more of a fluorescent color but in the shade it becomes the orange color that stands out very well against the black. You can see this in the middle pic. All the needles were painted with the same paint so the direct sunlight makes the needles brighter.

Couldn't find my plastic polish so I had to put the clear cover plate back on with just a washing off.

Re: 78 K20 modernization project
 

Next up will be to finish assembling the Camaro tach cluster. I finally got another printed circuit to replace the damaged one on the housing I modified to fit the third gen Camaro tach so now I can go forward with the assembly & wiring on it.

This thread got me started on it about a year ago.

http://67-72chevytrucks.com/vboard/s...ht=camaro+tach

I also picked up a spare Camaro tach face with the 80 psi oil pressure gauge I need to I can finish the overlay with an 80 psi range to match. The newer tach out of an 89 Camaro has a smooth face too where the gauge is not separate so it will lend itself better to a full gauge overlay like I did playing around with the speedo.

I may try to make the tach overlay look more like a stock speedo face with the circular stripe in the middle if I can make it fit so it would match up better with a stock speedo.

I think doing it this way and keeping the Camaro oil pressure gauge in place and just making your own fuel level gauge to go in the stock truck oil pressure gauge location is much easier and looks better too.

I may mess around with a stock oil pressure gauge and see if I can make it function as a fuel level gauge without having to change out the mechanism.

Re: 78 K20 modernization project
 

Good looking project. Did you have to swap the sending unit to use the 80 psi oil gauge?

Re: 78 K20 modernization project
 

Yes. I installed the 80 psi sender to match. They are marked on the hex section at the base of the sender with a 60 or 80 so you can tell them apart.

I still need to change out the temp sender but didn't have a 1/2-NPT to 3/8-NPT reducer handy. The diesel sender is smaller than the older small block sender. The newer heads have smaller sender bosses so it would bolt right into a newer engine with the lighter casting scalloped edge cylinder heads.

Re: 78 K20 modernization project
 

Good looking project

Re: 78 K20 modernization project
 

Just a note, Idle mixture screws do not change the over all air fuel mixture off idle.

Re: 78 K20 modernization project
 

That is what the wide band oxygen sensor bosses on my exhaust are for.

The wide band gauge is the best tuning tool I ever purchased.

I need to put it on this truck and get the jetting dialed in but it is too darn cold to go outside to play.