1966 300 convertible help!!

66chry300

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Hi all! Working on a 1966 chrysler 300 for a friend of mine and I am having a lot of trouble with the brakes. This car is 4 wheel drums and I tried converting over to a dual master cylinder, but it is not working correctly. The master cylinder is off a 1967 300 and I have the front port going to the original distribution block. The rear port goes directly to the 3/16 brake line for the rear brakes and I capped it off at the distribution block. The problem is that the back brakes are getting too much pressure causing them to overheat. The front brakes work, but it feels like the rears are doing most of the work. Is there something I can do to try to correct this or should I just replace the master and convert it back over to a single line master? I really would like to have a dual line master on this car but if I am not able to I will just convert it back to original. Thanks for your help!!
151AD681-0E09-4C85-A6AF-9A336B1A0C75.jpeg
 

Lefty71

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I think you need a proportioning valve, correct for you application. Is this still full manual??
 

CBODY67

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NO proprtioning valve on the power drum brake cars, ONLY with front disc brakes. You need to mimic the 1967 plumbing. Might need the appropriate pre-bent tubing from a repro supplier.

The distribution block is mainly there to turn on the "BRAKE" warning light should one end of the car lose brake pressure, no more, no less.

FWIW, the Chrysler disc brake cars did not plumb the same as GM front disc brake cars did. So consult the '67 FSM for how the '67 Chryslers were plumbed and go from there.

Hope this might help,
CBODY67
 

'66 Fury I

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The rear port on the master cylinder should be connected to the front brakes and the front to the rear. The factory system with 4 drums and dual master cylinder does not use a proportioning valve. It does use a safety switch which is used to control a warning light on the dash in case of a loss of pressure in one side of the system. This valve is often mistaken for a proportioning valve. I believe that if you switch the supply lines, the problem will be solved. Hope this helps. Lindsay
 

3C's & a D?

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I believe you may need the correct disc/drum distribution block, or possibly go through the original drum/drum distribution block. I'm not sure, but if you're getting too much pressure in the rear, possibly there's a "restrictor" or something in the block that might balance them out?

@Ross Wooldridge ?
 

Ross Wooldridge

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1) To start, the Bendix booster is for discs - you need the drum booster. Show us a pic of your booster to be sure you have given it the right name...
Your booster should look like this:
65-68 drum brake booster.jpg

2) As noted above, mimic the 67 plumbing - from the dual res master to a distribution block, NOT a prop valve. Your new master cylinder should be one with balanced reservoirs, NOT a later dual res one with a larger rear reservoir (for front brakes).
Your new master cylinder should look like this:
1666582031964.png

Your new metering block should look like this:
1666582125657.png

3) Lift up the rear of the car until the wheels are off the ground (use jack stands or a hoist for safety), and back off the rear drum adjusters until the shoes are barely making contact with the drums when the wheels are rotated.
4) Lift up the front of the car until the wheels are off the ground (use jack stands or a hoist for safety) and adjust the front drums until the shoes are barely making contact with the drums when the wheels are rotated.
5) Adjust the pushrod from the booster (ensure you have the correct booster) until it holds the master 1/16th of an inch away from the booster mating surface before bolting it down. This ensures the correct preload of the system. Too much, and you'll engage the brakes early - perhaps even all the time - making the fronts overheat and not grab properly, and when you do want to stop, this may make the rears do all the work and overheat themselves.

I hope this helps.
 

Big_John

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Hi all! Working on a 1966 chrysler 300 for a friend of mine and I am having a lot of trouble with the brakes. This car is 4 wheel drums and I tried converting over to a dual master cylinder, but it is not working correctly. The master cylinder is off a 1967 300 and I have the front port going to the original distribution block. The rear port goes directly to the 3/16 brake line for the rear brakes and I capped it off at the distribution block. The problem is that the back brakes are getting too much pressure causing them to overheat. The front brakes work, but it feels like the rears are doing most of the work. Is there something I can do to try to correct this or should I just replace the master and convert it back over to a single line master? I really would like to have a dual line master on this car but if I am not able to I will just convert it back to original. Thanks for your help!!View attachment 564290
First, the rear port on the MC feeds the front brakes and the front port feeds the rear brakes. You need to switch those.

That said, it doesn't seem to me that the rear brakes should overheat because of that. One cause we've seen a few times is a bad hose holding pressure on the brakes. Another is the push rod length sticking out too far. I would also make sure your emergency brake isn't hanging up and the brake adjusters are hooked up correctly.

As said, there is no proportioning valve in a drum/drum system. I've done a couple conversions.... For one I used a distribution block from a '69 (or so) B-Body as a convenient way to connect everything up. I've also used the block similar to what @Ross Wooldridge has posted and that worked real well too. I wouldn't call it a "metering block" though. I think that came from Inline Tube or one of the companies that build replacement brake lines. It's a pretty simple block... Just gives you a good place to connect your lines.
 

stubs300

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1) To start, the Bendix booster is for discs - you need the drum booster. Show us a pic of your booster to be sure you have given it the right name...
Your booster should look like this:
View attachment 564348
Jesus Ross, can you read or just read what you want to read? Just because he says he has a Bendix unit doesn't mean he has a Bendix, WHEN HE CLEARLY STATES THAT IT'S THE ORGINIAL!

It has a Bendix brake booster on it. It is original
 

Ross Wooldridge

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It always pays to check. The Bendix booster is not original to a drum/drum system and may have been switched out.

A photo of what he has will answer any questions...

... and respectfully, what are you jumping down my throat for? We're just trying to help this guy and to do that we need to clarify information we might not be sure of.

There's a way you could have asked that question of me that was less stress inducing.
 
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3C's & a D?

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I was going to ask if it was a late night for you Ross? As you posted a picture of the drum/drum master cylinder, that's not like you.

And yes, @66chry300 , we need some actual photos of the parts you're using. A picture is worth a thousand words!
 

Ross Wooldridge

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As far as I understand the original poster wants to convert single pot master cylinder for a drum/drum system to a dual reservoir master cylinder system. He made no mention of switching to discs, unless I missed something.
 

Ripinator

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It always pays to check. The Bendix booster is not original to a drum/drum system and may have been switched out.

A photo of what he has will answer any questions...

... and respectfully, what are you jumping down my throat for? We're just trying to help this guy and to do that we need to clarify information we might not be sure of.

There's a way you could have asked that question of me that was less stress inducing.

Ross: You have been Stubbed. . . Twice! :poke:
 

Ripinator

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Hi all! Working on a 1966 chrysler 300 for a friend of mine and I am having a lot of trouble with the brakes. This car is 4 wheel drums and I tried converting over to a dual master cylinder, but it is not working correctly. The master cylinder is off a 1967 300 and I have the front port going to the original distribution block. The rear port goes directly to the 3/16 brake line for the rear brakes and I capped it off at the distribution block. The problem is that the back brakes are getting too much pressure causing them to overheat. The front brakes work, but it feels like the rears are doing most of the work. Is there something I can do to try to correct this or should I just replace the master and convert it back over to a single line master? I really would like to have a dual line master on this car but if I am not able to I will just convert it back to original. Thanks for your help!!View attachment 564290

Hey! nice car and nice color. Do the power windows work?
 
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66chry300

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Think I figured out the issue! Turns out this isn’t the original booster and it’s actually for a 66 Chrysler with disc brakes! Just going to convert it back to a single line since it’s near impossible to find the correct booster.

CB6D5FE5-1A62-4864-BFC3-C245562568EE.jpeg


5D9CC056-B2E0-4230-A2C0-0D65E17C0BCF.jpeg
 
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