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

[Nick_R_23]

Getting down to the little things now!

Ran the vent lines for the fuel tanks and rear axle.



Ran the harness for the new license plate lights.



Adapter for the 7 pin trailer connector.





Made an interior harness for the trailer brake controller that tied into the brake light switch.



Made a circuit breaker block for the power feeds for the 7 pin and brake controller.



Driver front brake line was pretty rusty looking at the fitting, so I made a replacement.



Perfect fit!

[Nick_R_23]

Started on the rear brakes today. Didn’t make it that far, mostly because I could’ve sworn up and down that I had 13” brakes, but turns out that I actually had 11” rears. Instead of returning all the parts and going with 11”, I’m going to locate the 13” backing plates and end up with a better set of brakes!

The original ones were destroyed…







Both wheel hubs stripped. Probably going to take these into town with me and have them hot tanked since they’re pretty nasty.

[OutlawDrifter]

That's the 11in "oil bath" RPO code, haha

[Nick_R_23]

Yeah no kidding.

I’m not sure if I mentioned this earlier, but for some reason I’ve had an interference issue with the hydroboost and master cylinder. I’ve had everything apart several times and can’t find any issues, so since I’m into the brakes now, I decided to just make a shim to gain the proper clearance back.

Sheet of aluminum measuring .058”. I used an SBC thermostat housing gasket as a template and just moved the holes out a little bit for the booster bolt pattern.



Perfect fit! With the shim in place, I can measure .007” clearance now between the pin and piston.



Still not sure why there was a clearance issue, but this turned out to be a nice solution!

[93M6Formula]

Interesting, so was it applying slight pressure to the MC without that shim?

[Nick_R_23]

Yeah, noticeable enough that I could slide the master cylinder onto the booster studs and seat it by hand and have nearly a washers’ width of gap between the two flanges once the pin touched the piston. I could feel it pushing the piston in if I pushed the master cylinder the final bit manually.

[Nick_R_23]

Rear wheel hubs after a couple rounds in the hot tank and a fresh coat of paint!

[Nick_R_23]

New bearings installed in the wheel hubs!



I need to pick up a press to install the wheel studs through the hubs and drums.



I scored a pair of early 13” backing plates! These were hard to find because they used the bolt in style parking brake cables.



Old junk removed!





Brakes completely redone on passenger side!





And brakes completely redone on the drivers side!

[OutlawDrifter]

Brass hammer and punch will get those studs driven in, but a press is nice to have as well.

[Nick_R_23]

Picked up a new toy!



All assembled! I’ve been needing one for a while and finally bit the bullet.



Pressing in the wheel studs



All the studs are installed



New wheel seals installed



Hub and drum assemblies completed!



Assembly installed and hub nuts torqued!



Cleaned and painted the axle shafts



As well as the axle flange hardware.



Axle all complete!



Picked up some new hardlines for the rear brakes



Also some retaining clips for the parking brake cables.



New hard lines on rear axle





New hardline for the rear frame also





New shocks for the rear!



Installed!

[OutlawDrifter]

Looking good!

[Nick_R_23]

I had quite the lame weekend on this one. I finally got the parking brake cables in, and intended on bleeding the brakes and installing the wheels, and maybe even getting a test drive in! The front parking brake cable went well, but the intermediate one turned out to be for a shortbed wheelbase, so I ordered the next size up.

Then, bled the rear brakes only to not get that great of pressure out to the rear. After vacuum bleeding the rears, and various troubleshooting, I could sometimes get pressure at the rear, and sometimes not. The proportioning valve was replaced quite a few years ago, but it’s acting like it’s sticking to one side now. I ordered up a new one and will try again next week!

[Nick_R_23]

Alright, after messing with it for a bit, this is where I’m at.

Went to adjust the rear shoes. I can tell the new drums are slightly out of round, as they drag slightly on the shoes on only about 1/2 of the drum. Both sides do this. However, at the adjustment sight windows at the bottom of the backing plates, the shoes have a small gap and don’t touch the drum. I could likely crank on the adjuster and force them to, but the drum would be locked up. It feels like the shoes touch the drum at the top before the bottom. The driver side is slightly better than the passenger side. Currently, I have it adjusted where there is some slight drag.

After attempting to bleed the brakes, the front worked fine. I could not get consistent pressure to the rear, although the rear brakes did work really well once sporadically. I determined the proportioning valve was shot. Ordered a new proportioning valve and the bleed lock tool for it. Installed both of those and had better results, but still inadequate pressure in the rear.

Warrantied out the brand new master cylinder for another one and rebled the system. Now I have good pressure to the rear. However, the hose from the frame to the axle was machined incorrectly, and the hard line wouldn’t seat and kept leaking. This damaged the new passenger side hard line. I warranted out the hose and reflared the hard line and replaced the fitting. Went to install and the drivers side threads pulled right out without even tightening down, damaging the driver side hard line. Replaced the hose again, with a different brand, and reflared the other hard line and replaced that fitting. Installed the new line and rebled the system again. Removed all the air and the pedal feels good.

However, if I have the pedal pressed I can still turn the rear drums by hand. They definitely drag more than what my adjustment was, but they definitely don’t work. Front seems to lock up solid and work great. For an extra brain scratcher, if I manually pull the parking brake cables by hand, both rear brakes will work perfectly via the parking brake.

Not sure what the issue is, but I think I’ll have to dive back inside one of these upcoming weekends.

At least I had some help, lol.





This was…interesting.



New proportioning valve installed



New wheels mounted in the front!

[OutlawDrifter]

Brakes can be very frustrating!

Sounds like the drums need turned to true and balanced before you chase any other issues.

Or just swap to rear discs?

[Nick_R_23]

Had to at least see what the wheels looked like on it!



I’ve been messing with the brakes more on and off. Ended up taking the drum assemblies apart to double check that everything was okay. Shoes appear to fit perfect.





I did notice that the shoe material stuck out past the metal portion, so I ground that down in case it was causing the shoe to not sit flat on the backing plate.





Still not satisfied with the brake performance, I hypothesized that I needed a K30 master cylinder instead of the K20 unit, which gave me 1-5/16” bore instead of the 1-1/4” bore, meaning I would have a higher volume output, stiffer pedal feel, and less pedal travel, which is what I think this truck needs. So I picked up a K30 unit.



Painted!



Bench bled the unit



Just out of curiosity for comparison - it appears the K20 and K30 units are slightly different depths.





After all of this, I’m still not completely satisfied. I’ve also determined that the hydroboost unit doesn’t appear to be always working as it should, so I’ve ordered a new replacement. Unfortunately, it has an up to 90 day lead time.

[Nick_R_23]

Made an unexpected score today! I found a rust free hood on Marketplace for $75!



Not perfect but damn close!

[OutlawDrifter]

Awesome find!

[Nick_R_23]

Alright, I’ve finally admitted defeat on these brakes. I’ve been through this system a hundred times and can’t come up with any reason why it won’t function. The new hydroboost unit should be here soon, and I ordered a Lugnut 4x4 rear disc swap kit with the larger 76-78 Eldorado calipers and all the upgrades, as well as a new Leeds disc/disc proportioning valve. I’ll have to swap out the master cylinder again too, but I hope this will be worth it to finally get the brakes where they should be.

[Nick_R_23]

The Lugnut4x4 kit showed up today!



As well as the Leeds disc/disc proportioning valve.



I’m waiting on the hydroboost to show up before I get a master cylinder, but I’m planning on moving to a 99-07 hydroboost master cylinder with a shorter 2000 S10 reservoir.

[Nick_R_23]

Stripped the axle back to a bare spindle



Pressed the studs back out of the hub and removed the drum



Reinstalled the studs with the brake rotor



Updated seal installed



Hub mounted and spindle nuts torqued and adjusted.



Caliper mounted





Passenger side also completed

[OutlawDrifter]

Looking good, brakes for as simple as they are, can be quite frustrating!

[Nick_R_23]

Picked up some new axle shaft seals and short brake lines.



Axle shafts reinstalled





Welded on the tabs and installed the hoses





Bent new hard lines





Installed the new disc/disc proportioning valve



Upgraded the rear exhaust hangers while I was under there.