8-lug front disk brake upgrade

[davepl]

I'd like to convert to front discs (currently power drums) but with 8-lug wheels there are not a lot of choices.

The owner I bought it from had collected the whole crossmember from an original disc-brake truck, and I could probably buy/get it from him, but then they're all 40-year-old parts I'd be starting with. By the time I rebuild the calipers and add new rotors and so on I don't know I'd be much ahead of all new.

The only one I could to date is here:

http://www.performanceonline.com/196...-DELUXE-16682/

However that kit says "C-10", and mine's a longhorn (so C-20). Also I don't see a master cylinder. Wouldn't I need a disc/drum master and junction?

If anyone has been down this road before, or if a vendor has parts, please let me know!

Thanks
Dave

[Daddy Brim]

I buy a lot of stuff from these guys http://www.classicparts.com/1963-70-...info/71-978S8/

[old Chevy guy]

You dont need to change the whole crossmember just the stuff from the ball joints out. The biggest thing is the spindle and the parts the caliper hangs on . You can still buy brand new stock roters from advanced auto parts. I dont know for sure but I bet the caliper can be bought new too If the guy has the roters and there not all pitted or worn out just have them turned like you would do if you were installing new brakes. Yes you would need a disk drum master too,also available stock,new. I also believe you will need a diffrent booster too. As far as the spindles what could really go wrong with them?

[davepl]

Originally Posted by Daddy Brim

I buy a lot of stuff from these guys http://www.classicparts.com/1963-70-...info/71-978S8/

Hmmm... only with drop spindles unfortunately, so far as I could find on their site. To each their own, but I like trucks at stock ride height, or at least that's what I intend to do.

I'm surprised noone sells a kit with booster and master... they seem to for the 5 and 6 lug kits, just not for the 8s. Unless the 8s have a bigger resevoir to begin with and don't need it, but I have to find a stock one to look at first...

[davepl]

Originally Posted by old Chevy guy

You dont need to change the whole crossmember just the stuff from the ball joints out. The biggest thing is the spindle and the parts the caliper hangs on . You can still buy brand new stock roters from advanced auto parts. I dont know for sure but I bet the caliper can be bought new too If the guy has the roters and there not all pitted or worn out just have them turned like you would do if you were installing new brakes. Yes you would need a disk drum master too,also available stock,new. I also believe you will need a diffrent booster too. As far as the spindles what could really go wrong with them?

So to be clear, the control arms are the same? Basically ball-joint-to-ball-joint?

Wonder why they would use a different booster? I guess discs do require a little more assist.

[Daddy Brim]

Did not realize that those were drop spindles, I to like a truck to be stock height. Give these guys a call. I do not know if they have what you want, but they can get you in the right direction.http://www.earlyclassic.com/home.aspx

[old Chevy guy]

Originally Posted by davepl

So to be clear, the control arms are the same? Basically ball-joint-to-ball-joint?

Wonder why they would use a different booster? I guess discs do require a little more assist.

This is what I have read here about the control arms. The booster thing comes from the fact that I was selling some and was asked if they were the same and asked around and was told they were not. That power disk was diffrent than power drum. Not carved in stone,just what Ive been told.

[67chevemall]

You don't have to have the booster. Early corvettes had disc with no booster.
You just have to push on the peddle. Just need a port valve after your master. I got the adjustable one from CPP that you can adjust the fronts by a dial.

[davepl]

You don't =need= a booster with drums either. But presuming I =want= a booster, the question is whether the same booster is used for disc and drums.

J70 is the Hydraulic Brake Booster option.
J73 is the Heavy Duty Hydraulic Brake Booster option.

So far as I can tell, for 1970:

1970 Series 10, Blazer 3970502 (Bendix 2508396)
1970 Series 20-30 (except #11000 axle) 3970503 (Bendix 2506422)

As I read it you basically either had a half-ton booster or 3/4-1Ton booster, with no differentiation between disc and drum.

[67chevemall]

Drums had no booster, so ..... booster would be disc.

[davepl]

Huh? You mean to say there's no such thing as power drums? I think here is where we'll have to agree to disagree.

[67chevemall]

Not that I have ever seen on chevy trucks

[FirstOwner69]

Originally Posted by 67chevemall

Not that I have ever seen on chevy trucks

Power drum brakes were an option on these years (until 1971 when front discs became standard). A large % of the trucks had them.

[67chevemall]

Wow makes no sense at all to have power drums... I guess that is why they changed to disc.
Any pics of a power drum set up?

[FirstOwner69]

Makes as much or more sense with drums. Less effort and more stopping power. Same reason boosters are used with discs.

[Daddy Brim]

I'm pretty sure your booster will work with disc brakes, but you will need to change the metering valve to the proper proportioning valve. I have the same power drums on my 67 C/20

[Mike C]

2 of my 3 '70 GMC 3/4 tons had power drum brakes. I did a disc swap on the big block truck and kept the drum booster. I pulled the booster from the other truck and am planning on using it for the disc swap on the '69 short step Chevy I'm messing with now.

[slobberdogs]

I have a stock set of spindles taking up space in my garage off my 72' c20. They're yours just need to figure out how to get them to you.

[RichardJ]

I put discs on my '67 3/4 using parts from a '76 1 ton that a guy was parting out. I took everything including the PS box which turned out to be bad.

There were a couple of differences that may not apply to your '70, if you are looking to change the complete cross-member.
there is an angled piece on both sides of the cross-member, that the upper A- arms bolt to and this is bolted to the frame rails. The '67 is a large cast piece and the '76 is a lighter piece of pressed steel. They compensated by adding an extra piece on the inside of the frame rails. When bolted together, the frame rail is sandwiched between the two. Only one of those bolt holes line up, if I remember correctly. One hole has to be drilled and others elongated. The bolts through from the bottom to the frame do line up.
I had taken both apart and picked the parts I wanted. I knew I wanted to keep the '67 springs, because the '76 was a big block. I kept the '67 cross member and added the '76 inside frame rail pieces.
Either the upper or lower A-arm and ball joint is the same - fits both 67 drum and 76 disc spindle. The other arm fits only the '76. Sorry, can't remember which I used. If you were planing on using both upper and lower from the '76, you're good. I did this six-seven years ago.

The '67 brake line crosses to the passenger side on the back of the crossmember. The '76 lines go to the radiator crossmember, where the combination valve is located. The line to the rear from the combo valve, goes along the passenger side frame rail to a brass inline connector, just past the bellhousing. My '67 has the exact same connector in the same spot. Unbolt all the lines from there forward and transfer to your truck. The flex lines go through the frame ahead of the axle, instead of behind on the '67. I think there may have already been a hole there that had to be enlarged.
The combination valve hanging off the side of the master cylinder looks too cluttered to me. The later location under the radiator such as on the '76 is a lot cleaner.

Be sure and check the lug sizes on the disc hubs. On the '76 I used, they were larger than the '67. I didn't want a mismatch or deal with getting new aluminum wheel lugs, so I replaced the studs in the disc hubs.
Hope that helps.

Be sure and get the sway bar. If you even have one, the later one will be bigger.

[lolife99]

http://www.performanceonline.com/196...-DELUXE-16682/

Stock height or drop spindle version.