what brake booster do i need - Impala Tech
Brakes & Suspension Conversion Questions & more

 
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post #1 of 8 (permalink) Old 01-16-2016, 08:28 AM Thread Starter
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what brake booster do i need

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ID:	13698[/ATTACH][/ATTACH]64 impala 327 ,car never had power brakes,,,,i have a duel master cylinder with disk on front....the booster needs to be small ,ive seen ones that stick out way to far in the engine bay,is that original for the 64 ,,,then there are duel boosters I think,,,and the vac to run it comes from ???? want to keep engine compartment as original as posible

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post #2 of 8 (permalink) Old 01-16-2016, 10:59 AM
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The factory used an eleven inch diameter single diaphragm brake booster that is going to push your master cylinder off the fire wall. It also requires a longer rod with a different end on the rod that may or may not be compatible with the master cylinder you have now. I would buy a proper matching master cylinder as the diameter of the cylinder inside changed going from manual to power assist as well.

You can buy all of the original parts as replacement service parts except the rod from Rock Auto dot com. Or you can look on line for a conversion kit that includes everything matched and placed in a box for you.

I have to ask why you are changing over to power assist? Power assist was offered as an option to little old ladies when they ordered an automatic transmission. It allows them to hold their varicose vein laden little legs on the brake pedal at a stop light so that the car didn't creep forward. Power Assist Brakes will not make the car stop in a shorter distance, or more frequently from a high speed. It just for holding a car still at a light or stop sign, or for disc brake applications where the line pressure is doubled compared to drum brakes.

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post #3 of 8 (permalink) Old 01-16-2016, 11:15 AM Thread Starter
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well everbody has power brakes,just thought I would power dem up
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post #4 of 8 (permalink) Old 01-16-2016, 11:18 AM Thread Starter
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well why not I have disk in the front
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post #5 of 8 (permalink) Old 01-16-2016, 11:52 AM
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Power assist with disc brakes will cut your leg effort in half. It won't make it stop any better but it will be easier on your leg to hold the brakes at a stop light without the car crawling up to nudge the car in front of you.

I have driven customers cars with discs and a big cam where no mater how hard I stood on the brake pedal (which has a 6:1 ratio) the car crept forward (bad combination of brake parts and poor cam choice for the street).

In the case of bad brake part choice they had retained a manual brake master cylinder when they added the power booster. There wasn't enough line pressure to fully activate the disc so only the rear drum brakes were holding or stopping the car. The big cam never generated enough manifold vacuum to power the diaphragm (it is the pressure differential between manifold vacuum and atmospheric pressure that makes the power assist work). In that case I took the power assist off the car as it wouldn't work with his cam and put everything back to manual with a smaller cylinder bore for disc brakes. Disc brakes require a minimum of 700 psi to even move the discs into contact with the rotor, 1,200 to begin to create friction. The pad composition at these manual brake pressure levels will also affect how well the car holds at a light. As does the heat in the system, as high performance metallic disc brake pads work better the hotter they get, stone cold they will barely hold.

There are a lot of variables to consider besides appearance when dealing with brakes. I am an engineer that also have had my own mechanical repair and Hot Rod shop to pay for my racing hobby. I research all of the variables involved before I buy the first part, as your brakes actually working are kind of important. I always follow the factories lead unless I am building an out right race vehicle, after which I look to the type of brakes used on other professional race cars (NASCAR, NHRA, SCCA) for the kind of racing I want to do.

I would recommend contacting Wilwood or Baer if you want to buy race car parts, and the Chevy Assembly manual for part numbers of the pieces that Chevrolet specified originally if looking to drive on the street. Since disc brakes didn't appear on full size Chevy's before 1967 you will need to look at 1970 and up to 1976 (when they went metric) for matching part numbers you can buy today.

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post #6 of 8 (permalink) Old 01-18-2016, 07:36 PM Thread Starter
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thanks for all that info but back to what I need,,just want plain jane power brakes,,the 327 is stock and it is not a race car,just tell me what I need
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post #7 of 8 (permalink) Old 01-18-2016, 09:20 PM
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An Assembly manual for a 1971 Impala would be my guess. I would first consult the 1964 Assembly manual to see if the factory offered Power Assist as an option back in 1964. Don't know if it did or not, but that is where I would start, then move on to the 71 were I know they did and it most closely matches you existing brakes (unless they are metric in which case 1985 Monte Carlo would be the Assembly manual to check instead of the 1971).

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post #8 of 8 (permalink) Old 01-22-2016, 09:05 PM
 
 
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I have 62 impala and I used master cylinder, brake booster from a 67 impala. Hope this helps.
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