Power Brakes in 69... pedal bumper or not? - Team Camaro Tech
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post #1 of 11 (permalink) Old Dec 19th, 11, 10:21 PM Thread Starter
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Wes
 
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Power Brakes in 69... pedal bumper or not?

On a 69 with power disc brakes (J52) did Chevy install a rubber bumper (stop) for the brake pedal or not?

I checked the AIM but it's no help here.

Thanks!
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post #2 of 11 (permalink) Old Dec 21st, 11, 08:08 AM Thread Starter
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Re: Power Brakes in 69,..pedal bumper or not?

Anybody?

I know that manual brakes had the rubber stop (bumper) for the brake pedal, but I seem to remember that maybe the power brake cars didn't.

Could somebody with original J-52 brakes (power assist brakes, front discs, rear drum) check to see if the pedal bumper is used. It's mounted on the steering wheel side of the pedal just above the plunger for the brake-light switch.

Reason I'm asking is, my front brakes are dragging a bit. I've filed 3/16" off the booster's push rod. I'm now thinking this bumper may the reason the front calipers aren't opening as much as they should.

Thanks!
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post #3 of 11 (permalink) Old Dec 21st, 11, 08:22 AM
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Re: Power Brakes in 69,..pedal bumper or not?

I recall they did not, but my memory may be faulty dragging brakes are something else entirely. In power brake applications, the booster to brake pedal rod is supposed to hold the brake pedal at a certain distance that does not even approach where the bumper is, that is why they did not need it. If your brake pedal is hitting the bumper, adjust the rod so it stops short of it.

as to the brakes dragging, when you mounted the master to the booster, did you have to push or use the nuts to close the gap? if so, that is your issue. You should be able to install the master onto the boster and have it seat completely without interferance. The nuts should just hold it in place. I had to grind quite a bit off the booster to master rod to get it fitting properly.

Kevin


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post #4 of 11 (permalink) Old Dec 21st, 11, 08:50 AM
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Re: Power Brakes in 69,..pedal bumper or not?

Just went out and checked mine and yes there is one there. Same as the one on the clutch but thicker most likely because there's not a return spring on the brake pedal so it hasn't seen a lot of work.

I was going to say the same thing as Kevin, just loosen the jam nut at the pedal clevis and turn the brake rod into it some which will effectively shorten it. Some boosters come with the pedal pushrod a little long and you have to trim some of the threaded end off.

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post #5 of 11 (permalink) Old Dec 21st, 11, 01:01 PM Thread Starter
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Re: Power Brakes in 69,..pedal bumper or not?

Steiner, you say "...just loosen the jam nut at the pedal clevis and turn the brake rod into it some which will effectively shorten it."

On the rod that attaches to the clevis which attaches to the brake pedal, I don't believe you can shorten the rod by turning it (threading it) into the booster. You can adjust the clevis a bit but not the rod.

Am I mistaken?

After filing off quite a bit off the master-to-booster rod, I was thinking my problem (brakes dragging) was on the pedal side of the equation.

Any other thoughts?
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post #6 of 11 (permalink) Old Dec 21st, 11, 01:36 PM
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Re: Power Brakes in 69,..pedal bumper or not?

He's suggesting that the rod going from clevis into the booster maybe preloading it. If that's the case then turning the rod into the clevis would relieve it.

Robert

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post #7 of 11 (permalink) Old Dec 21st, 11, 01:43 PM
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Re: Power Brakes in 69,..pedal bumper or not?

Yes you can turn the rod itself into the clevis (which will pull the pedal toward the firewall), until the rod hits the pedal that is. Much easier than taking the clevis off the pedal and spinning it.

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TKO 600-Moser 3.42-Detroit Truetrac
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post #8 of 11 (permalink) Old Dec 21st, 11, 08:05 PM Thread Starter
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Re: Power Brakes in 69,..pedal bumper or not?

Quote:
Originally Posted by Steiner View Post
Yes you can turn the rod itself into the clevis (which will pull the pedal toward the firewall), until the rod hits the pedal that is. Much easier than taking the clevis off the pedal and spinning it.
Ahh,..yes. I thought you saying the rod could be threaded into the booster to adjust.

And yes, I've threaded the clevis as far as it will go.
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post #9 of 11 (permalink) Old Dec 22nd, 11, 06:04 AM
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Re: Power Brakes in 69,..pedal bumper or not?

As far as it will go down the threads or has the rod hit the pedal now? You can trim the rod if it hits the pedal with the pedal still against the hard stop.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
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post #10 of 11 (permalink) Old Dec 22nd, 11, 12:20 PM Thread Starter
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Re: Power Brakes in 69,..pedal bumper or not?

Brother Steiner,..yes, the pedal is hitting the rubber stop now, which is why I started this thread. The rod (on the pedal side of the equation), can't be trimmed, obviously.

If the factory didn't use the thick rubber bumper, perhaps my pedal would have another 1/4" travel. On the other hand, I don't want the brake-light switch to serve as the pedal stop.

...which is why I asked how 69's, with power discs, were configured from the factory (with or without the rubber bumper?).
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post #11 of 11 (permalink) Old Dec 22nd, 11, 01:39 PM
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Re: Power Brakes in 69,..pedal bumper or not?

Quote:
Originally Posted by Straight-line-69 View Post
Brother Steiner,..yes, the pedal is hitting the rubber stop now, which is why I started this thread.
I asked if the rod was hitting the pedal arm, not if the pedal was hitting the stop

.....
Quote:
Originally Posted by Straight-line-69 View Post
The rod (on the pedal side of the equation), can't be trimmed, obviously.

If the factory didn't use the thick rubber bumper, perhaps my pedal would have another 1/4" travel. On the other hand, I don't want the brake-light switch to serve as the pedal stop.

...which is why I asked how 69's, with power discs, were configured from the factory (with or without the rubber bumper?).

Yes, the threaded pedal rod can be trimmed.
1. Is the clevis bottomed out at the end of the threads now?
2. If not, is the end of the the threaded pedal rod inside the clevis hitting the arm of the brake pedal?

If the answer to 1 is no and 2 is yes, then you can just cut a half inch off the end of it. That way you can turn the clevis down the rod further (or turn the rod into the clevis more) which again pulls the pedal more towards the firewall until the end of the rod again hits the pedal arm.

If the booster pedal rod is a mile long you still only have about an inch or so that you can screw the clevis on before the end of the rod hits the pedal arm. That's why you have to find out where you need the pedal and trim the rod accordingly. Dremel or hacksaw works fine.


If the rod is out of thread and the clevis is bottomed out the only option is to run a die down the rod to cut some more threads in it.

'69 Camaro
Dart 400-AFR 195-224/224 HR-Powerjection III TB with F.A.S.T. Sportsman XFI
TKO 600-Moser 3.42-Detroit Truetrac
500hp/538lbft

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'02 Z/28 vert-stock-sold and totaled

Last edited by Steiner; Dec 22nd, 11 at 02:03 PM.
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