I just installed a SSBC vacuum pump in my chevelle. I am wondering if I did something wrong since me pedal seems hard. I also installed a accumulator as well. I ran a line from the pump the the accumulator, I also ran a line form the manifold vacuum to the accumulator. then from the accumulator I ran to the brake booster. the booster is a 8" dual diaphragm. Is there a good way to test the system to makes sure it is working correct? I feel my pedal is very hard.

any ideas?

You need a check valve in the manifold-accumulator line to isolate the manifold from the rest of the system. You want to use the engine to override the pump whenever possible, but the pump will never be able to deal with the manifold. I use check valves from a Volvo.

Thanks, I talked to my Dad and he said the same thing, I did not even think of a check valve there.

will the push rod being to long cause a harder pedal. I got the pump to work now. the pedal is quite firm, but not to bad just wondering if I could make it better?

The pushrod in the booster or the pushrod that goes to the pedal?

I could be wrong but on my car I thought on the booster that I bought (came assembled) that there was only one push rod. But I guess either one if there is two. I had almost no brakes, so I adjusted the clevis on the pedal to make it longer. Now it is a bit firm maybe I will just back it off a bit and see if that works.

what else could cause a hard pedal?

I talked with the booster guy and he told me that I need 17" of vacuum. the pump should be at 24". what else could it be? I really need help on this one.

what else could cause a hard pedal?

I talked with the booster guy and he told me that I need 17" of vacuum. the pump should be at 24". what else could it be? I really need help on this one.

Master Power Brakes has an excellent FAQ section with answers like the following:

I have manual brakes and I have an extremely hard pedal. Why?
Check the bore size of your master. If it is larger than 1" then you will have a very hard pedal.

Can I use a power brake master without a booster?
Usually not. The bore size will be too large giving a hard pedal and the piston hole will be shallow allowing the push rod to fall out.

What are the symptoms of a bad power booster?
A bad power booster will give a very hard pedal, it will feel like you need two feet to stop the car.

How much vacuum is needed to operate a booster properly?
For a power booster to function properly you will need at least 18" of vacuum at idle in park. Anything lower will give you a hard pedal.

What happens if the vacuum is too low?
If your vacuum level is too low you will experience a hard pedal and it will feel like the vehicle won't stop. Install our AC2724K Electric Vacuum Pump to maintain a constant 20" of vacuum.

http://www.mpbrakes.com/technical-support/reference.cfm

THANKS!!!!!!!!!!!! that is really helpfull!!!

Gives me some things to check out

interesting find.. I put a vacuum gauge on the check valve and got 24" of vacuum. I then put it back on the booster and had the same pedal. Pulled the vacuum gauge of the booster and still had the same pedal. I think it is the booster.

An easy way to test the booster is to press the brake pedal down when the engine is off then start the car. The pedal should move further down after the vacuum from the engine has been applied.

Well I took it apart and I think that the master is bad since there was brake fluid in the booster bore. I am guessing that that makes the booster bad as well.

Ok, well I just wanted to follow up on this.

The master is good, the booster is good. the problem was that i had a deep master and a shallow booster. So I was only making contact at the very end of the stroke. I made a spacer and it seems ok now, I still need to bleed the system again just to be sure but I think I am good