1" Master vs 1-1/8" ?

[pitts64]

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[tumper93]

No, the problem you are having is normal for a vehicle with low vacuum even with a canister. You are depleting the vacuum in the canister and you are just manually holding the vehicle with the master when you do finally stop. There is no solution to avoiding this unless you make shorter stops, or go to a hydraboost. I went through this with mine before I put it on the road and finally found this out. If you sit at a stop light and apply, let up, apply the pedal like on a stock vehicle the same thing will happen.

[speED]

I agree, your low vacuum is causing the hard pedal. When you are driving and suddenly close the throttle plate vacuum increases due to the fact that piston speed is still fast (brake pedal will feel good). As the engine idles down and piston speed decreases with the throttle plate closed vacuum will decrease causing the hard brake pedal.

[pitts64]

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[tumper93]

You could switch to manual if you want, but you currently have a system that works, so if it were mine I would just leave it unless you are wanting to remove it just to make it have a "cleaner" look.

[pitts64]

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[tumper93]

The fittings are reversed. Front port is for rear brakes and rear port for front brakes. I don't know my Pontiac history but GM used a booster on the 67-69 Z28 302 too and it had terrible vacuum! Guess they weren't that concerned over the actual power assist, considering most rides were manual then anyways, the little assist present would have been a step above what was reddily available at the time. Everything is power today so we are spoiled!

[David Pozzi]

pitts64,
On your vacuum reservoir there is a fitting on the top center of photo with the other end of the hose connected to the booster. The fitting up top looks like a check valve but if it is a check valve it's backwards to air flow. you should have a check valve from engine to reservoir to prevent the reservoir from losing vacuum back to the engine when you accelerate.

David

[pitts64]

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[pitts64]

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[wedged]

all other things being equal, the smaller bore will yeild a softer feeling pedal with more travel and an increase in system pressure.

[pitts64]

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[Apogee]

My brake pedal ratio is 9:1
I'm undecided between manual, vacuum pump or Hydroboost...I have to do something. I drive my car at least 20,000 miles a season and this brake problem is just asking for it with these hills around here....

Does anybody make booster check valves for low vacuum conditions?

A check valve doesn't create vacuum, it only checks what vacuum you have available from the engine. If that's virtually nil, no amount or type of check valve is going to help your situation. You need more vacuum from the sounds of things.

Tobin
KORE3

[pitts64]

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