33 replies to this topic

[S pack]

^^^^ Agree James. Getting the booster tested by a brake specialist should be the next step IMO.

[UCSLE]

take the one way valve off the booster and check it first , probably not the problem but its the easiest thing to start at 

[rexy]

Rexy, do you mean to run electric pump to booster, no engine vac? Do i still need cut -off switch?/ Thanks Paul

Correct. 
You have a closed system with vacuum hose that contains the booster and the switch - switch reads the vacuum in the booster and switches on and off as required.

The pump is connected into this system with a one way valve in the line between the pump and the booster closed system. This valve only allows air to flow out of the booster system. Air out = increased vacuum.

 

If you have less than 10 inches of vacuum from the engine then a vac pump will produce a marked improvement in brake performance.

 

One persons big cam is another’s economy grind….

[I'm a Red Motor fiend]

Also agree with James. I have standard rear brakes, HQ discs and calipers and a reco double diaphragm booster.
264 @ .050", .600" lift, 105 LSA and I still stop ok.

[rexy]

Out of interest what manifold vacuum does it make?

[lctriples]

around 8" but as other forum members have suggested, i will start with booster first. My local brake dealer said they cant test but might shop around, as i have mentioned earlier, dont want to waste money if not booster problem, paul

[dattoman]

8" is not enough

18" is the norm

You def need more supply

[UCSLE]

was the booster connect when you got 8" ?

 

Vacuum leaks will cause low vacuum

 

block the boosters hose if the engine vacuum rises the boosters leaking

[lctriples]

No i just connected vacuum guage to carby spacer outlet, (engine vacuum)