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I was helping my friend install a brake booster on his 65 charger. After changing the old manual brake MC and adding a new booster, we bled the brakes. still had a soft pedal. so we bled the MC on the bench, and bled the brakes again. felt good to me, but still no brakes. after a week of bleeding we took it to a brake shop. the guy told us we did not have enough vacuum. I had hooked up the vacuum directly to the intake, thinking I would have full vacuum. I found a fitting on the intake with a rubber cap, so I assumed this was a vacuum port. Now I am thinking this was a temperature port or something. am I correct? could this 383 with a moderate sized cam have a vacuum issue I do not know about or am i just not hooked up to the correct vacuum port. It has a demon carb so I am guessing the rear port on the passenger side is constant vacuum?
 

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First take a reading of the engine's vacuum with a vacuum gauge. You will need 18" of vacuum to operate power disc brakes safely. If you have less than 15" install a vacuum pump.or switch to manual disc brakes. You can go to the junk yard and get a complete vacuum pump system off an old car. Look for a port on the front side of the throttle plate of the carburetor that has full time vacuum to hook up the vacuum gauge. On the back of the carburetor look for the 3/8 port. this is used for the PCV valve. On the intake behind the carburetor their should be a 1/2 NPT x 3/8 hose fitting for the vacuum hose for the booster. This is used for the vacuum for the booster only.
 
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