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Discussion Starter #1
my car had manual brakes so when i converted my v6 to a v8 i added the power brakes from the donor vehicle. now when i step on the pedal it's like stepping on a cement block. the pedal moves maybe two inches with alot of effort. what could it be?
 

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Something I learned here was several guys re used the rubber boot over the manual master cyl. If you put the boot over the rear of the booster, air can't get into the rear of the booster to push on the diaphram. = no boost.

There usually is a felt pad to filter the air going in to quiet operation and keep the bugs out.
David

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The older I get, the faster I was!
 

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Discussion Starter #3
i don't understand. the master cylinder connects to the power assist with bolts. then the power assist connects to the firewall, and there is a rubber boot going through the firewall that the pedal connects to. what rubber boot on the master cylinder are you referring to, could you explain what to do better? thanks.

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Shure,
On manual brakes there is a rubber boot on the firewall. This boot goes tightly around the pushrod that connects to the brake pedal.
On power brakes there is no boot on the firewall.
On power brakes there is a plastic bellows tube that connects the rear vent hole in the booster to the passenger compartment.
When you step on the brake pedal you are opening a valve that allows atmospheric air to come from inside the car and into the rear portion of the booster, pressing on the diaphram. Usually you hear a whoosh, when steping on the brakes, that's the air going into the booster right around the pushrod.
If you block the air from entering the rear of the booster you will not get any boost.
Several people who have posted here have added power boosters and left the firewall boot covering the booster rear opening and had no boost until they removed the boot.
David

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The older I get, the faster I was!

[This message has been edited by davidpozzi (edited 06-17-2000).]
 

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Discussion Starter #5
there is a rubber boot coming through the firewall, but it has holes in the back. when the engine is not running, i hear the whoosh when i step on the pedal. when the engine is running, there is no whoosh. this tells me it has something to do with the vacuum. what do you think?
 

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The rubber boot is incorrect. You need the white plastic tube between the booster and the firewall. It is $18, but being able to stop could come in handy.
When I put a booster on the manual brakes in my hardtop, I was very careful not to bend or crimp the tubing going to the Tee-block.(which would be very easy to do). My convertible has and extra loop in the tubing going to the front of the Tee-block, so bending this tube unintentionally would be more difficult.
 

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Check your vaccum line from booster to manifold. It probably sucks shut somewhere when a high vaccum is reached. This hose needs to be of special stiff vaccum hose not regular hose.
The booster rear opening up under the dash should be about 1 1/2" to 2" diamiter, not two holes. There usually is a felt pad around the pushrod to muffle the whoosh.
David

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The older I get, the faster I was!
 
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