I am working with a 68 camaro, with the stock front disc, rear drum, power brakes. The problem is it feels like there is no power, it feels like power for the first inch of travel, and you can hear the power booster when you press down, but then it gets super stiff, and you can't press the brakes anymore, making the brakes suck. Are the rear drums adjusted too tight? what else could it be?

I'm sure you've taken the car for a short voyage and applied brakes while rolling, quite the difference between being stopped and rolling.

Brakes will be stiff sitting still. Let there be a minute or two between application of brakes, this let's the residual pressure bleed off and the fluid come back into the master cylinder via brake shoe return spring pressure.

One should be able to press on pedal with engine off, keep applying pressure, start engine, pedal should sink to floor.

Release pedal, brakes should be normal.

Are you making enough vacuum?

If you think rear drums are too tight, jack a wheel up and turn it to see if too tight.

------------------
Everett 68/350/PG/11.90/115mph

Agree with what Everett said, how does it feel when actually driving? Also, you mentioned being able to 'hear' the booster... exactly what are you hearing? If it is making any kind of hissing noise or sound of air escaping, then I'd say either bad booster or bad check valve on the booster. You should be able to pump the brakes several times, then go and pull the valve out of the booster and hear the hiss of pressure escaping. If not, start there...

Bill C.


------------------
Bill C.
Colorado Springs, CO

68 Camaro... someday!
71 Chevelle SS
70 Nova

I am having a suspicious problem with my brakes right now too, and I swear I can hear hissing from the booster, or somewhere. Are you saying that when you hit the brakes, car off, everything connected that there should be no "air" escaping from the booster? Seems reasonable, I did not even think about this. The valve on the booster should be a check valve, no?

Mark

------------------
69 SS, Stroker 489, Tremec TKO, Tight Road Suspension

Yes, it is like this when i am driving not sitting still, I can hear a wooshing noise from the booster like they usually make. could the brakes in the back being too tight make this happen or no.

One will hear a whoosh when pressing pedal.

Master vac, has a diaphram inside, vacuum on one side, atmosphere on the other.

When pedal is depressed, opens a valve to allow engine vacuum to pull diaphram into M/C. The other side next to firewall, has a bleed hole to allow air to rush in when diaphram moves.

Release pedal, vacuum valve closes, atmosphere valve opens to allow diaphram to return to original position.

Now, if pedal depression is hard, as in no engine running, then master vac is bad.

There is a valve in the vacuum line between the engine manifold and master vac, this is a one-way check valve, called anti-backfire valve. In case of backfire, valve closes to protect master vac from damage. Make sure this is installed correctly and that it does work, good seating in one direction and good flow in the other direction.

Make sure the vacuum pick off point is at the base of the carb/manifold rather than at a runner, this will hinder the amount of vacuum "made". One cylinder would be generating vacuum verses all eight cylinders as a source.

If engine is running, and brakes are applied heavily, does the engine stumble, miss, or run rough as in a vacuum leak? Diaphram could have a crack in it. If engine runs normal, then I would suspect the vacuum valve inside master vac broke.

If you think the brakes are dragging, one person should be able to push the car with relative ease, providing the tires are inflated and round. Should not be a load on the engine if in gear.

Hope this helps, maybe some others here will chime in....

Everett

Yes, everything you said makes sense, the valve is good, the vacuum source is good, the brake pedal is very stiff when the engine is running no way it would even get half way down. There is no stumble from the engine, it must be the power booster

sounds like the booster to me too. my 81Z does the same thing. and I have narrowed it down to the booster. I just have not had time to replace it. I idle with 12to14 vac. my brakes realy stink. expecialy when it is cold. even when vac is up their still not right.

Everette: Nice explanation, makes sense. Ihave a question on my car though, I am getting a really soft pedal rather than a hard one, with a new 7 inch booster. I assumed that the outlet port (vacuum connection) on the new booster had the check valve, but I don't think that it does. Question though, if I disconnect the hose at the booster, I feel air rushing out as I pump the pedal. I blocked it and tried it again, the pedal pressure got alot stiffer. I thought I had it figured out, but the more I think about it, I think I have the logic in reverse.

Anyway, if I have the MC on or off, the pedal pressure seems the same, almost like it is not accuating the MC at all. With the MC off, I can see the shaft moving in and out, but didn't check to see if it was doing so with appreciable force.

Any ideas?
Mark

------------------
69 SS, Stroker 489, Tremec TKO, Tight Road Suspension

You are correct, Mark. There will be air rushing out the vacuum connection if not connected and you pump on it. Move the diaphram, move air.

Check the depth of the M/C actuation rod hole from the M/C mounting flange. Transfer this measurement to the master vac M/C mounting surface and adjust the rod to within .020-.040 inches shorter. You may be pressing the pedal, but too short of rod will not actuate the M/C.

Install the check valve in the correct direction on the vacuum supply line.

Flattop might want to add a vacuum cannister, master vac's generally like 15 inches or above for good response, however, I have seen some with less than 10 inches work well.

Let me know what is happening....

Everett

[This message has been edited by Everett#2390 (edited 03-28-2002).]

This may sound silly, but you can adjust the actuation rod in the booster, right? I assumed (stupid me) that it would have come from SS Brakes already optimized, as I bought them as a set (booster/MC). I noticed the rod had a threaded piece in it that looked like it was for adjustment. I'll take another look at it tonight, and report back when I know something.

Thx,
Mark

------------------
69 SS, Stroker 489, Tremec TKO, Tight Road Suspension

Well, I took Everette's advise on checking the clearance between the pushrod on the booster, and the piston on the MC. Turns out that this is the problem, brand new part from Stainless Steel Brakes. I called them, they asked me to send the booster back to them, that this is nothing I can fix in the field. Wonderful. Another week without my car. I have had so many problems with the new parts I have bought during this engine swap, it is amazing. So much wasted time.

Thanks again for the help.
Mark

------------------
69 SS, Stroker 489, Tremec TKO, Tight Road Suspension