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Brake booster size

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Old 04-17-2012, 01:54 PM
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Brake booster size

Finally getting around to pulling the old single pot master off of my '66 slick.

I'm adding a front disc setup from a '79 but don't have the '79 master cylinder and booster. I seem to recall that the '79 had a fairly large (think 11") booster so I'm thinking about buying one of these.... 1957-1972 Ford Truck 8" Brake booster 1 1/8" bore master cylinder w/valve | eBay

So a coupla questions arise....
1. Is it a huge deal to change booster size in this application?
2. How critical is it to match the master cylinder and brake booster to the calipers?
3. Am I correct in that the booster size dictates the pressure to the calipers and if so is my answer dependent upon what I intend to haul with the truck?

a bit more clarity of the configuration, Front disc: '79 , rear drums: '66

Thanks folks!

Last edited by Spyderjohn; 04-17-2012 at 02:00 PM. Reason: clarity
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Old 04-17-2012, 01:58 PM
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I would say if at all possible just get the master cylinder for a 79 just so that you know that you staying within the original application
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Old 04-19-2012, 12:01 AM
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The '66 Bendix vacuum booster in F100"s was 7", which was matched to the '66 drum/drum setup. M/C had a 1" bore. Bore size also affects braking, altho' in 1966 both manual and power assist brakes used the 1"

Booster got larger as years went by. There have been several articles written on later model truck and hot rod forums about matching booster size with braking capability at the wheels.

With regard to booster size, remember if you get too large, esp. with a 352 V-8, you will have a hard time getting the left valve cover off, altho, you can probably put that 8" on there and get by.

As I recall, a dual diaphragm 8" yields same power as a 9" single
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