Which brakes ?

[Bernie]

This is a question that I posed on the 67-72 message board a few days ago. I didn't get much response, and it is pretty technical so I thought I'd try again here.
I have a 69 K20 and the axles off a 78 with discs in the front and a 14 bolt rear. I'm looking to buy a master cylinder, booster and proportioning valve. What set up do I need ? I know that one off a 71 would work with the push rod that I have (but I don't know if it's Delco or Bendix). On the other hand, which master is used on a 78 depends on the size of the rear brakes. I would be very grateful for the advice of anyone who has done this axle swap . Thanks

[Scrub]

I have done the swap twice

On mine I took the proportioning valve from the donor that mounts on the crossmember just in front of the engine and I also got the steel lines to plumb it up. From what I know about the swap, that is the most important part, getting the P-valve from the newer year truck.

I don't think there is much difference in boosters unless you go to the Hydro-boost, which is hydraulic and powered off the the power steering pump. I don't think you need that, On both my swaps, I just used whatever booster I had.

What axle do you have up front? D44 most likely. I think you should be able to get a master cylinder for the 78 application at a good parts house, but It will need the original P-valve to be something other than Frankinsteined. Yours should be easy as the axle combo was a stock application and very common.

One conversion I did has a 1-ton front end that has huge bendix calipers (same as a Dana 60 but 2wd), so mine is different from yours. I went into NAPA and orderd a master cylinder for a 1-ton truck. It works OK but the rear brakes don't get enough fluid when I have a really large load.
IT was suggested that I get a Wilwood adjustable proportioning valve.
http://www.wilwood.com/products/valves/valves.asp
I really thing the Dana 60 requires a Hyrdo boost.

Good luck

[Bernie]

Thanks for the reply. I do have a D44 on the front and I do have the origonal proportioning valve. My main concern, if I go with the 78 master cylinder, is that the push rod from the brake pedal would be the wrong length and that I'd have problems fitting the MS to the firewall. Did you have any difficulty with this ?

[BLAZERMAN]

I have a dana 60 front with a 14 bolt 1 ton rear and am using the prop valve, master cylinder and booster from a 71-72 model K-20 truck and it works great. I also know of several others who have switched to the later model axles and run the same setup with no problems. The 71-72 prop valve is for disc and drum combo and the front calipers are pretty much all the same between the early and late models.

[Bernie]

Thanks Rob. I did some checking around. It seems that the master cylinder and booster for the earlier and the later, larger (JB7), setups are exactly the same. I thought to go with the later proportioning valve.