[Amc-list] 1970 brake specs?

["Swygert, Francis G MSgt 436 CES/CECM" <Francis.Swygert3@xxxxxxxxxxxx>]

Date: Thursday, February 22, 2007 02:33 PM
From: Tom Jennings <tomj@xxxxxxx>
Here's one for you: 1975-up brake "combo valve":
* auto-resets the warning switch after bleed or repair
* contains rear-brake pressure hold-off (stem on the end) eg.
   proportional valve.
It can be identified by the little pull-out spring loaded stem
on the left end.
Does that last mean you don't need the check valve in the master
cylinder port for the rear brakes?
------------------

NEGATIVE!! All it means is that there's a little pull-out spring loaded
stem on the left end. The spring is NOT inside the brake line port. It's
part of the proportioning valve. After the preset pressure is reached
the valve won't let additional pressure pass. The spring effectively
cuts off flow to the rear brakes after the pressure setting is reached.
When pressure is reduced the valve opens and pressure is released back
to the master cylinder. I don't know the exact internal plumbing, but
that's pretty much the way it works. I'm not sure why the external stem,
except maybe to release the valve if it should get stuck open. Depending
on exactly how it works, a stuck valve could leave the set amount of
pressure in the rear brake line even after the brake pedal was released.


------------------
Here's another one:

* Many cars have different drum shoe *widths* in the same wheel
   -- I thought it was a typo at first but it's consistent across
   many years. (Leading shoe narrow.)
-----------------

I've noticed the same thing. I've seen one set that had different widths
front and rear, but forget what it was on! I did a brake job for someone
and picked the parts up first. I opened the box and told the clerk
something was wrong -- the widths weren't the same! He got another box
-- same thing. So I took them. Both of us figured I'd be back, but the
originals were the same. Seems like it was a mid 70s Hornet or Gremlin,
but I can't be sure -- to long ago, and that's the only one I ever ran
across with two different widths. Many have different LENGTH linings on
the front and rear shoe though. 

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