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Discussion Starter #1
Hi Guys
I have a 65 Mustang that the previous owner converted from drum drum to disc drum.
Looking at the master cylinder, I see that the larger front outlet (1/2”?) is connected to the rear brake line, and the smaller rear outlet (7/16?) is connected to the front brake line.
Is this the right way round? I ask this because, even with an inline restrictor on the rear line, the rear wheels lock before the fronts..
Any advice is gratefully welcome!
 

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The front outlet with the smaller reservoir should go to the rear brakes and the aft outlet with the larger reservoir should go to the front brakes.
 

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Hmmm… Your description sounds as though there is no proportioning valve. A restrictor won't do. Without a proportioning valve in the rear line, you might die. Your car will die.

Use an adjustable proportioning valve. Practice stopping on a gravel road, adjusting until the front brakes lock slightly before the rear ones do. This is important.
 

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Hmmm... It seems the PO did a banged up job on that conversion. It would be much much safer to get that braking system right. Maybe some pix could help figure out what is going on? Also do you have power braking?

AFAIK, the 2 front brake lines should connect to the Distribution Block. The rear line connects to the Proportioning Valve then from the PV to the DB. 2 lines, front and rear, go from the DB to the MC. The rear line feeds from the small front bowl and the front line feeds from the rear larger bowl.
 

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Discussion Starter #5
Hi Guys
Thank you so much for your advice and guidance. Looking at my system again, this is what I can consider:
I do have power brakes (servo)
The car originally had a single outlet master cylinder that went to all 4 wheels that had drum brakes.
The PO upgraded the front from drums to discs and installed a dual outlet master cylinder.
The smaller front reservoir, with what looks like a larger dia. brake line is connected to the front brakes.
The larger aft reservoir with what seems to be a smaller dia. brake line is connected to the rear brakes.
I found the back wheels were locking up😱, and so installed a restrictor in line to the rear brakes which has improved but not solved the problem.
737368
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Thanks
 

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The smaller front reservoir, with what looks like a larger dia. brake line is connected to the front brakes.
The larger aft reservoir with what seems to be a smaller dia. brake line is connected to the rear brakes.
This is backward and must be reversed at once. The larger reservoir is meant to operate the large front disc brakes. Nothing you do will solve the problem until this is done.
 

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All brake lines should be 3/16.
Small front bowl on M/C to rear brakes.
Large rear bowl on M/C to front brakes.
Ditch the restrictor.
Use a proper proportioning valve in the rear line.
 

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As said above, your braking system is right now a disaster waiting to happen and absolutely needs to be done the proper way. No kidding, this is your safety that is in play. NPD has an adjustable PV / distributor block for about $60 that is really good and would fit the bill quite well. Get some inverted flare unions, some 3/16 steel tubing and proper fittings and route the lines as they should. You may need to add a residual pressure valve (10PSI) on the rear brake line to keep the pressure on the drum springs. Those can be found at Summit for less than $20.

You may want to look around your place and see if you can find a mechanic shop specializing in classic cars and ask them to get a look-see and maybe some advice. If they are cool they should be helpful.
 

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In your original post you said the front reservoir was connected to the rear brakes and the rear reservoir was connected to the front brakes.
Then you changed it to the opposite.
So which way is it?
 

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Discussion Starter #10
My Mustang is now just stationary eye candy until I sort the brakes out.
Thank you all for the good advice.
 

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Discussion Starter #11
Yes AWHTX, I'm sorry. The situation was as in the second post.
But today, I changed it so the rear, larger reservoir is now connected to the front brakes, and the smaller front reservoir is connected to the rear brakes.
Took it for a test drive since it was a little damp and slippery, and the rear brakes still lock up. So I will be ordering parts as per Wildpat's advice.
 

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Is your master cylinder for a front disc, rear drum setup. I had a kit put on my wife's 65 Vert and it would lock up the brakes when applied. It turned out the wrong MC was sent with the kit. After replacing it, no more lock up.
 
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