To boost or not to boost

[h3towel]

I bought whitby's brake booster, and I'm about to use it as a shot-put. I haven't been able to get good braking with it. When I remove the vacuum hose, it's much better. With the hose on, I have no brakes. Any ideas. About to say f-it and go back to the original brakes that came with the kit.

[wallace18]

Sounds like a defective booster to me.

[BradCraig]

Honestly, once i got my brakes properly bled they work great without a booster. Not sure I would want boosted. Willwood is in the future but still manual.

[h3towel]

I'm just curious as to why the pedal sinks to the floor when the vacuum line is attached, but not when it isn't. The check valve is fine from what I can tell. Even if the diaphragm was messed up, I can't see how the pedal would go all the way down.

[Norm B]

A few questions. Did you change back to the OEM brake pedal? Is the 3/8 spacer between the booster and the foot box front? Did you adjust the pushrod between the booster and master cylinder so it just allows the master cylinder piston to fully retract when the brakes are released?

[h3towel]

I used the brake pedal supplied with the kit from Whitby. I purchased the spacer from replica parts instead of the crappy spacers that were provided. It looks much cleaner this way. I hadn't originally adjusted the pushrod, I just followed the directions that came with the kit. After talking to Jeff Kleiner, I did adjust the pushrod. I had to have the rod that goes between the pedal and the booster (don't know the technical name) machined to make the rod adjustable. As it was, the brake pedal was really close to the firewall and below the height of the throttle pedal. I could have adjusted the throttle, but then I would have only had 1 inch of travel from idle to WOT.

[CraigS]

Any car w/ a vac booster, if w/ engine off, you pump the pedal a few times to use up the stored vacuum, you get a firmer slightly higher brake pedal. If you fire up the engine the pedal will become softer and lower. That is completely normal. But going all the way to the floor is not normal.
"As it was, the brake pedal was really close to the firewall and below the height of the throttle pedal." This is not normal either. Can you adjust the the pushrod that attaches to the pedal to raise the pedal? It should be maybe 6 inches from the firewall. Note also that your total pedal travel should be close to centered on a vertical pedal arm. In this drawing the MC would actually be your booster.
https://live.staticflickr.com/7815/32942260888_10b4597061_z.jpg (https://flic.kr/p/SbZGtj)20190120_154338 (https://flic.kr/p/SbZGtj) by craig stuard (https://www.flickr.com/photos/152454123@N04/), on Flickr
The idea here is that beyond a certain angle the point where the pushrod attaches to the pedal arm has too much vertical change w/ pedal movement and can cause problems.

[h3towel]

The existing pushrod that attached to the pedal was not adjustable. That's why I had it machined to make it that way. Essentially, it's 2 pieces now that screw together to raise or lower the pedal height. I'm honestly thinking about removing the booster and going back to the original brakes that came with the kit. From talking to other people, stopping is easy even with non powered brakes. Eventually, I'll get the wilwood upgrade and make it even easier. Before I go back to non powered brakes though, I plan on going to a hot rod shop near me and asking them to quote me a price to make it work.

[frd2]

They system definitely works when installed properly and everything working properly. (and works really well)

Don't give up too soon - hate to see you go backwards now that you have done all that work.

It is interesting that it sounds like your push rod is too short. Mine was originally too long (would not release the brakes fully - eventually locking them up)

Good Luck

[CraigS]

Are you out of adjustment to bring the pedal up? My thinking is this. Let's say a good pedal is 6 inches from the floor at rest. Engine off and pump the pedal several times and it is right there, real solid w/ almost no free play. Fire up the engine and now the pedal will drop 1.5 inches when you press it w/ pressure equal to an average stop. So it's still 4.5 inches off the floor. But, if your pedal is at 3 inches from the floor due to a too short push rod, when it drops 1.5 inches that feels terrible because it's only 1.5 inches from the floor and the angle is really messed up. Also, I reread your thread and notice you have a spacer between the firewall and booster. This will definitely lower the pedal. Is it needed for clearance?

[h3towel]

The spacer is required so the u-joints on the steering rack can spin. Without the spacer, the booster causes it to bind