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

[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.