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Keane165's 1970 LeMans

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Adding Booster to Drum/Manual Brakes


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Hey Pontiac people, 

I have a question. I have a 72 Lemans that has Manual Drum Brakes all around without a booster. 

Questions is can I install the booster I have(Came from 70 Lemans with Disk Brakes) onto my car? I thought that I would have to change the brake cylinders but when I go to find replacements, that don't specified if they are for a booster or not.. My apologies if this is a topic already, I tried to search but didn't find it. 

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Hi Fatony,

First of all, are you just looking at add the booster or convert the car to front disc brakes? Conversion to front disc brakes takes a few more parts, but having a booster is a good start. That's why I ask the question. What is your goal here? Maintain the stock drums or convert to front discs? I own a '72 Lemans with factory front discs.

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The endgame is to convert to disc down the road, but I only have the booster for now. I'm aware of the other parts needed, I'm look to do more work to the front end at hat time, (i.e.-front shocks, spring, ball joints, etc.. ) So being that i have the booster now, could i use this to improve the drum brakes until i do the conversation? I'm concern for the current brake cylinders, will they handle to booster? 

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The short answer is yes you can add a booster to your existing drum brakes. However for safety's sake, I would hope your existing master cylinder is a dual reservoir unit and not a single reservoir unit like a lot of them were in the 60s. The other consideration is to insure that your engine is producing enough vacuum to work the booster. 18 pounds of vacuum is typical - 23 pounds max.

The only other questions I would have is will your current master cylinder bolt up to the booster cleanly ? Also do you think you have enough flex/slack in the existing brake lines to push the master cylinder forward because of the addition of the booster? These are questions only you can answer when you try to connect everything up.

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You are MUCH further ahead money wise/safety to pickup a conversion kit, and JUSTA go disk in the front.   Kit will include: master cyl, booster, proportioning block, spindles, rotors, calipers.   Number of kits out there with different prices.  Do your home work.  Ask if the kit comes with the booster to pedal rod.  I had to make my own.  Ask about booster size.  I had to return twice and they finally sent the 9in booster I ordered originally.  The rest were too large for my GTO and HIT the valve cover.  Measure yours for the correct size.  Now is a good time to replace your front rubber lines.  More than likely they are 48 year old rubber.  Going through the work to install whatever booster you have there is Justa waste of time.  It will all be replaced when you do convert to disk anyway.   But adding pressure to things such as the OLD rubber lines.....not a good idea.

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