Front Disk Conversion Grabby Brakes

[eagleone1983]

Can someone tell me what the brake booster push rod should be set to on a '73 Front disk brake system? I have a '69 but it's retrofitted with Dr. Diff's front disk conversion kit. It's been on a few years and this year the brakes were spongy so I bled them.

The brake pedal travels quite a bit before the booster seems to kick on and when it does it'll throw you through the window. Today the fronts locked up on me and I'm tired of having to have the touch of an angel when braking Any help is greatly appreciated.

I'm only assuming maybe it's the push rod, I never adjusted it when I installed the kit. The kit included the recommended proportioning block.

 

[steve340]

To get a nice high pedal the pushrod should have around 5 to 10 thousands clearance.
Just enough to let the master cylinder fully return back.

 

[kramer]

A friend of mine has a 69 Charger with the factory power 4 wheel drum brakes and that car is scary when u barely touch the brake petal it will about send you through the windshield, I believe his problem is something is screwed up in the power booster unit itself.

 

[steve340]

Sometimes people loose the booster reaction disc and then the brakes can become very sensitive.
Also then the booster pushrod is now to short and when you apply the brake the booster shoots forward and eventually "slams" in to the master cylinder.
Google search brake booster reaction disc and all the info can be found.

 

[Ron H]

This booster gap gauge is very handy, saves a lot of futzing trying to obtain the measurement. Was your conversion from manual to power brakes? Ask as if it was, there is the pedal ratio adjustment involved. This can involve resetting the pedal linkage connection at the pedal arm. Also if converting from manual to power, the MC bores are non-compatible. Maybe not your hassle.

If you haven’t adjusted the prop-valve, this might be part of your hassle. There’s a lofty way to do this with pressure gauges or the trial & error method as I’ve done by driving the car on a preferably gravel or sandy surface with a partner outside to observe braking action. Front or rear tires skidding? Readjust the valve and try it again…and again. Could be too much action from the front or rears more noticeable on a loose surface.

 

[Ron H]

Booster Gap Gauge

 

[steve340]

The above tool is an very good one. It takes all the guesswork out of setting the booster pushrod.

 

[eagleone1983]

Sorry got busy and just getting back to this. My original system was power disk and converted to the Dr Diff front disk with all the options such as proportioning block, master cylinder, and booster. I never touched the push rod though.

Where do you get that tool?

 

[eagleone1983]

Sorry got busy and just getting back to this. My original system was power disk and converted to the Dr Diff front disk with all the options such as proportioning block, master cylinder, and booster. I never touched the push rod though.

Where do you get that tool?

Nevermind they are all over Amazon. So I understand how the system works. Does that mean my pushrod probably isn't long enough since I push the brake pedal down a quite a bit before it really grabs a lot?

 

[steve340]

It could be missing the reaction disc? or yes it is too short.
Or you have a low pedal for some other reason - air etc.
Get the pushrod adjusted correctly first.