HELP!!. No brakes after engine swap.

C

Chetly

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Aug 6, 2003

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Aug 29, 2004

#1

• Aug 29, 2004

• #1

Before i changed my motor i had normal brakes. After i now have rock hard brakes that are impossible to stop the car. My cam has a lobe separation of around 110*. My new carb and intake dont half the provisions for half the vacume lines. Should i just plug these open lines. Carb has mech. secondaries and manual choke. What can i do to stop my car, the E brake is getting old.

 

jrichker

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#2

• Aug 29, 2004

• #2

Vacuum leaks will make your power brakes useless, the booster must have 14 inches of vacuum to provide assist for the brakes.

Fix all the leaks by capping all the unused open vacuum lines. Then check the brakes & repost. The vacuum line for the brakes comes off the vacuum tree up by the windshield wiper motor. Make sure you have good vacuum there. Vacuum gauges are available at Autozone for about $18, you may want to get one.

 

88stangmangt

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Nov 25, 2003

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Aug 29, 2004

#3

• Aug 29, 2004

• #3

vaccum leaks will kill your motor.............something must be takiing the vaccum away from your booster......

 

BlackGT89

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Dec 16, 2002

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Aug 30, 2004

#4

• Aug 30, 2004

• #4

Also "big" cams can kill your vacuum at idle. You may need to purchase an aftermarket vaccum canister from Summit or Jegs, etc.

 

D

Daggar

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Jul 19, 2004

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#5

• Aug 30, 2004

• #5

You might also consider going to a boosterless brake master cylinder.

 

dastang2

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#6

• Aug 30, 2004

• #6

Daggar said:

You might also consider going to a boosterless brake master cylinder.

Click to expand...

then he would have the same problem. non power brakes and they suck. never are you supposed to leave vacuum lines unplugged. you also don't need an aftermarket vacuum canister. if you have driven some of fords older trucks and cars you might notice something that looks exactly like coffee cans with a nippled and a vacuum hose going to it. that is a vacuum canister and it is a cheap item at any junkyard.

 

D

Daggar

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#7

• Aug 30, 2004

• #7

dastang2 said:

then he would have the same problem. non power brakes and they suck.

Click to expand...

That's not exactly true. Non boosted master cylinders use larger pistons to increase the mechanical advantage and make pedal feel lighter. Though they are not as easy to depress as a vacuum assisted unit they are no where near as hard to operate as a vac assist that doesn't have any.

 

dastang2

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#8

• Aug 30, 2004

• #8

i used to have a 71 f100 swb with non power brakes and it sucked big time, esp. if somebody pulled in front of you, how does just a little bit of vacuum help make the brake pedal feel about 40 pounds lighter.

 

D

Daggar

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#9

• Aug 30, 2004

• #9

dastang2 said:

i used to have a 71 f100 swb with non power brakes and it sucked big time, esp. if somebody pulled in front of you, how does just a little bit of vacuum help make the brake pedal feel about 40 pounds lighter.

Click to expand...

It's simple. The booster is a large diaphram with lots of surface area... and lets say you have 14 psi of vacuum over a suface area of 10 inches connected to a linear actuator (the one that pushed in on the master cylinder plunger) that's 140 lbs of pressure that is assisting you (when the brake pedal is pressed and opens the valve to the booster) in operating that actuator.

EDIT: the numbers I used are just for example.

 

DTT92LX

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Oct 28, 2003

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Aug 30, 2004

#10

• Aug 30, 2004

• #10

Here's how the vac asst brakes work:

http://auto.howstuffworks.com/power-brake1.htm

 

D

Daggar

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#11

• Aug 30, 2004

• #11

DTT92LX said:

Here's how the vac asst brakes work:

http://auto.howstuffworks.com/power-brake1.htm

Click to expand...

Great find DTT92LX

 

dreddstang

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Aug 26, 2002

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Aug 30, 2004

#12

• Aug 30, 2004

• #12

Hey Chetly,

Just check all your vacuum lines going into your intake. A few years ago I swapped an Explorer GT-40 intake onto my old T-bird and when I was done I had the EXACT SAME problem as you. I simply had the vacuum lines hooked up in the wrong spot. Fixed it instantly.

Don't go buy a new super-booster before you check your vacuum line placement from the intake to the tree! Good luck, let us know what happens!