Has anyone done a rear disc conversion on an 8-lug?

[FLYNAVY30]

Id really like to upgrade the rear drums to discs on my C20 while retaining the 8 lug. Has anyone done this successfully? I havent been able to find any conversion kits for the rears, so Im assuming it'll have to be done with factory front parts and a little backyard engineering.

[Chevyland]

Originally Posted by FLYNAVY30

Id really like to upgrade the rear drums to discs on my C20 while retaining the 8 lug. Has anyone done this successfully? I havent been able to find any conversion kits for the rears, so Im assuming it'll have to be done with factory front parts and a little backyard engineering.

Go to blackbirdscustomtrucks.com , I just bought, and put on there rear wheel disk conversion for an eaton ho72 on my 72 longhorn c30. My mechanic put them on in no time and they work perfect. I think the kit costs about $400 or so. Good luck

[bigmac73]

Originally Posted by Chevyland

Go to blackbirdscustomtrucks.com , I just bought, and put on there rear wheel disk conversion for an eaton ho72 on my 72 longhorn c30. My mechanic put them on in no time and they work perfect. I think the kit costs about $400 or so. Good luck

if i go with the rear disc kit, do i need to change my porportioning valve?

[FLYNAVY30]

I believe so, but dont quote me on that

[Longhorn 70]

Originally Posted by bigmac73

if i go with the rear disc kit, do i need to change my porportioning valve?

you are supposed to. at first I didn't change mine when I did the front conversion. it stopped much better after I did the proportioning valve. I imagine you'll get a gain in performance out of the rear when you change the valve.

[Longhorn 70]

Go to blackbirdscustomtrucks.com , I just bought, and put on there rear wheel disk conversion for an eaton ho72 on my 72 longhorn c30. My mechanic put them on in no time and they work perfect. I think the kit costs about $400 or so.

That's WAY cheaper than just replacing bad drums and bearings!! Did you get the kit that has an emergency brake? I also wonder if they play nice with stock rims. Not trying to steal or hijack but I need new drums for the HO52 and this is something I've considered.

[c20pickup]

i believ you can use the backing plates and some other hardware off of a 14 bolt ff. but hell if theres a kit available like the one above, go for it! i just found the gold mine thanks chevyland! now i can have 4 wheel discs

[FLYNAVY30]

awesome thanks! Ill check it out

[Chevyland]

Hey guys, they do work with stock rims I did not get the e brake option because when I talked to the guy at blackbirds he asked me if I use my ebrake much, and if I didn't , don't get the ebrake option because it will be more maintenance since it uses another caliper. As far a I am concerned it was my only option since most brake parts are no longer available for the ho72, but also the work it took to do the conversion was no more work than it would have taken to do a brake job even if I could have got the parts. If I remember right he also has an option for flexible hoses that you need to weld a tab on the axle and a piece of flex hose extends to the caliper since it is not right against the axle like the original back of the drums are. If you call the guy a blackbirds he will answer all your questions. It definitely works!

[425HP409]

Texas law requires an operable parking brake to pass the annual safety inspection. Check the laws in your state before you eliminate your parking brake.

[c20pickup]

Originally Posted by Chevyland

Hey guys, they do work with stock rims I did not get the e brake option because when I talked to the guy at blackbirds he asked me if I use my ebrake much, and if I didn't , don't get the ebrake option because it will be more maintenance since it uses another caliper. As far a I am concerned it was my only option since most brake parts are no longer available for the ho72, but also the work it took to do the conversion was no more work than it would have taken to do a brake job even if I could have got the parts. If I remember right he also has an option for flexible hoses that you need to weld a tab on the axle and a piece of flex hose extends to the caliper since it is not right against the axle like the original back of the drums are. If you call the guy a blackbirds he will answer all your questions. It definitely works!

what kinds of calipers and rotors does this system use? I saw it said he wouldn't separate parts from the kit, so what happens when I need to replace calipers, I supposes I could have the rotors machined once or twice, but what about the calipers?

[jhama78]

Originally Posted by c20pickup

what kinds of calipers and rotors does this system use? I saw it said he wouldn't separate parts from the kit, so what happens when I need to replace calipers, I supposes I could have the rotors machined once or twice, but what about the calipers?

From my experience working on off road rigs with rear disc conversions... aftermarket rear disc brake brackets typically use 73-87 k10 front calipers.

The e-brake calipers they list are more than likely caddillac eldorado calipers with an integraded mechanical ebrake.

my 2 pennies.

-j-rod

[Iron Hauler]

I used Ruffstuff brackets on mine and bought everything else at my local auto parts store. I have less than 300.00 in it with all new parts.

[Bigdav160]

If you register your truck as an antique, you don't need the inspection.

Swamp Rat documented his brake install down in the 4x4 build section.

[WIDESIDE72]

Originally Posted by Bigdav160

If you register your truck as an antique, you don't need the inspection.

Swamp Rat documented his brake install down in the 4x4 build section.

They put emergency/ parking brakes in vehicles for a reason. Letshope you never find out why!

[jhama78]

Originally Posted by FLYNAVY30

Id really like to upgrade the rear drums to discs on my C20 while retaining the 8 lug. Has anyone done this successfully? I havent been able to find any conversion kits for the rears, so Im assuming it'll have to be done with factory front parts and a little backyard engineering.

Since you are in the Hampton roads area I'd talk with Tim over at Shakerbilt in Chesapeake. He makes disc brake brackets steering and other parts for trucks. Mainly offroad trucks, but the brake kits will cross over.

http://www.shakerbuilt.com

When ya talk to him, let him know that -j-rod sent ya.

[FLYNAVY30]

Will do! Thanks everyone for the info

[Bigdav160]

DIY4X also sells brackets and calipers

[Longhorn 70]

it appears that most use the 71-87 ¾ ton front calipers. I wonder if the 90-96 big brake Corvette rear calipers will work. That way you could have ebrake and 4 pistons.

I have sent a request to ruff stuff to ask this.

[Longhorn 70]

Update: Ruff Stuff reccomended the 77 El Dorado rear brake calipers.

[c20pickup]

what do we change the prop valve to? I know if you put front discs on you have to use a prop valve from a truck that originally came with discs. so if w put 4 wheel discs on would we have to use a prop valve from a newer truck or one from a Cadillac?

[k2rm]

I bought Blackbird's kit with the 77 El Dorado cailpers with parking brakes a few years ago. I originally used a disc/disc GM master cylinder with the stock 9" dual booster. I also used an adjustable valve for the rear and a 5 PSI residual valve. If you look online, it is recommended that a 5 lb residual valve is used for the el dorado calipers because of the parking brake spring retracting the pads from the discs. The residual valve keeps the springs from retracting too far.

When I first set up the system, the braking sucked. It was unsafe. The issue with the el dorado calipers is that you have to properly adjust the parking brake to so that the pads are close enough to the discs so that the rear line can actually build pressure. My problem was that I would adjust the parking brake, get a couple good stops, and then the calipers would be out of adjustment. I fought it for about a year. I finally spoke with someone who said many of the rebuilt calipers don't have rebuilt piston ratchet mechanism, therefore the pistons won't hold their position after a few braking attempts. One of the calipers I received from Blackbird was such an improperly rebuilt or defective caliper.

I went to Napa, bought a new caliper, installed it, and now the truck stops very quickly and extremely straight. The parking brake also holds very well. I had been driving this truck for 20 years with the stock drum/drum combination and can definitely say that this has been a very good upgrade.

After my experience, I believe that it is poorly rebuilt calipers that give the El dorado parking brake calipers such a bad reputation. Also, the rear residual valve is also overlooked. Standard calipers don't need the residual valve and therefore it is assumed the Caddy calipers don't need them either.

I now have a Wilwood 1 1/8th master cylinder with their adjustable proportioning valve. I think that being able to adjust the rear is also important to get the proper rear bias.

[c20pickup]

Originally Posted by k2rm

I bought Blackbird's kit with the 77 El Dorado cailpers with parking brakes a few years ago. I originally used a disc/disc GM master cylinder with the stock 9" dual booster. I also used an adjustable valve for the rear and a 5 PSI residual valve. If you look online, it is recommended that a 5 lb residual valve is used for the el dorado calipers because of the parking brake spring retracting the pads from the discs. The residual valve keeps the springs from retracting too far.

When I first set up the system, the braking sucked. It was unsafe. The issue with the el dorado calipers is that you have to properly adjust the parking brake to so that the pads are close enough to the discs so that the rear line can actually build pressure. My problem was that I would adjust the parking brake, get a couple good stops, and then the calipers would be out of adjustment. I fought it for about a year. I finally spoke with someone who said many of the rebuilt calipers don't have rebuilt piston ratchet mechanism, therefore the pistons won't hold their position after a few braking attempts. One of the calipers I received from Blackbird was such an improperly rebuilt or defective caliper.

I went to Napa, bought a new caliper, installed it, and now the truck stops very quickly and extremely straight. The parking brake also holds very well. I had been driving this truck for 20 years with the stock drum/drum combination and can definitely say that this has been a very good upgrade.

After my experience, I believe that it is poorly rebuilt calipers that give the El dorado parking brake calipers such a bad reputation. Also, the rear residual valve is also overlooked. Standard calipers don't need the residual valve and therefore it is assumed the Caddy calipers don't need them either.

I now have a Wilwood 1 1/8th master cylinder with their adjustable proportioning valve. I think that being able to adjust the rear is also important to get the proper rear bias.

thanks for the detailed response! what p/n was the wildwood master cylinder? was it a custom piece or one made for the 67-72 chevy 3/tons?

[k2rm]

This is the one I bought. It is universal fit.

http://www.summitracing.com/parts/wi...556p/overview/

It is the 1 1/8 bore which works great with the dual 9" booster. You may need a smaller bore size if you have a different booster or have manual brakes.

It also comes in powdercoated black or unpolished. The only reason I went with the Wilwood master was because I was tired of the leaky caps on the stock units. The Wilwood is screwed down and I have never had a leak. The GM master worked just fine otherwise.

This is the adjustable proportioning valve:
http://www.summitracing.com/parts/wi...1179/overview/

I mispoke about the 5 lb residual valve. It was the 10 lb valve. I installed it near the frame rail.
http://www.summitracing.com/parts/wi...3279/overview/

[FLYNAVY30]

has anyone ever run an independent hydraulic style parking brake? My buddy and I were messing around with the idea of a separate, smaller caliper (think drag racing brakes), mounted to the front of the rear discs. The e-brake pedal would have a very small, separate master cylinder, almost like a clutch master cylinder, and just pressurize those two smaller calipers and lock them in place. We were just tossing around ideas as Ive never had good luck with the cable operated parking brakes