Disk brakes 80/800's

[Doug Rasmussen <76075.2276@domain.elided>]

Matt Adler asked how to convert his Dana 27 front to disk.

   Here's the deal.  Your front diff was made by Dana.  Any Dana-made disk
brake backing plate that uses a six bolt mount should work on your
differential.  Note: the Scout II's used 8 bolts, so that won't work.  The
backing plates I used were from a '75-'76 chev PU.


Conversion method 1:
  Parts-wise, the easiest way to do the conversion is to have your Dana
27/30 hubs machined flat on the back side.  Disk brake rotors are fitted on
the back of the hub, while brake drums are fitted to the front of the hub. 
Your drum brake hubs are only machined on the front for the drums, and not
on the back since disk brakes were not available in the early years.  From
the comparing I've done, it appears drum and disk hubs are the same except
for the machined back side.

  Once the hubs are machined, you mount new Scout II rotors.  That takes
care of the rotor situation.  All the Scout parts places should have new
rotors available.

  Now the disk brake backing plates are mounted in place of the original
drum brake backing plate.  When you do a trial mounting, you'll notice the
Chev caliper has a clearance problem with the closed knuckle portion of
your diff.  A small part of the casting has to be ground or machined away
to clear the caliper.  Not a big deal, just a little has to be removed for
the clearance.

  In my case, on my '67 800,  the Chev brake hoses connected without any
adapters just like the originals.  I assume 80/800's all used the same size
lines.

  That's about all I can think of.  It's not a big a job, finding someone
to do the machining of the hubs will be the hard part.  


Conversion method 2:
  There's another way that doesn't need to have the hubs machined.  This
way requires a little more parts scrounging though.  You can use Scout II
disk brake hubs that are already machined flat on the back, but in this
case your spindles have to be replaced with spindles off a Scout II drum
brake Dana 30.  The Scout II used larger diameter spindles so you have to
replace the spindle before the Scout II hub will fit.   When you change to
the Scout II spindles  new bronze bushings will have to be custom machined
to replace the needle bearings in the Scout II spindles.  The Scout II Dana
30 used a larger diameter outer axle than the earlier Dana 27/30's did. 
Without the new custom bushing, your early model axles won't have any outer
support.

  Method 2 may be more expensive.  The Scout II disk brake hubs (new) are
about $50/ea.  You'll have to find someone that has the Scout II drum brake
spindles off an old Scout.  The spindles shouldn't cost much, they aren't a
sought after item (unless all the early Scout guys start converting to
disk).

  Method 2 has the slight advantage that you end up with the heavier duty
wheel bearings that were used on the Scout II's.

  The stock master cylinder worked fine on my '67.  I didn't change over to
a power brake master cylinder.


  
  Either way the conversion is done, the results should be the same. 
You'll be able to make a panic stop without having both feet on the brake
pedal.

Doug