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Discussion Starter #1
I'm converting Dees67 from manual drums to power drums. I bought a reman booster/MC from
AutoZone a few weeks back and got it on the car last week. This weekend I went to fit new lines
from the distribution block to the MC and discovered that the front port on the MC has a larger
threaded fitting than the rear port, which is 5/8". This larger port has me concerned that I might
have been given a MC for a power front-discs/rear-drum setup. So can someone who's been
down this road help me out with these Qs:

1. Does a larger port fitting automatically mean more pressure?

2. I thought the front (closest to radiator) port on a MC is usually connected to the rear brakes
and vice versa. If so, why would the larger port on the MC be in the front?

3. Did power drum brake cars use the distribution block that has the low pressure switch in it?
All the vendors I've seen list that switched block as a disc brake block.

4. If this IS a power disc MC, can I use it on my power drum setup? Do I need to make any changes
to the system to do so? Should I return it to Auto Zone?

Signed,
Stumped in NH...

Rich
'67 C-code 'vert (Dees67)
'69 GT FB (project car)
Check out my band: Brickyard Blues
 
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The size of the fittings is only so that you cannot mix up the lines on the original application. Only the piston bore of the master makes a diff on pressure
Drum brake masters has residual pressure valves built into them on both ports . Masters for disc/drum only have a residual valve in the drum brake port

Greg B
 

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Discussion Starter #3
How can I tell if a port has a check valve in it? And I thought the check valves were for
disc brakes and that drums brakes did _not_ have the check valve. But from what
you're saying, I've got that backwards?

Rich
'67 C-code 'vert (Dees67)
'69 GT FB (project car)
Check out my band: Brickyard Blues
 
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How can you tell? Without taking the brass seat out of the outlet port? The residual pressure valve is just a small one-piece molded rubber flapper under the brass seat in the outlet port.
You cannot see them.I have an old drum brake master from a 69 in the garage. To test to see if it had RPV's in the ports I used a small diameter blunt probe and inseted into each port. I can feel the resilency of the rubber in the base of the port. I really don't advice doing this as too much force from the probe might damage the valve.
I would just double check the application with Autozone and if its the correct # just install it.

Greg B
 
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