66 Power Brake Issue

[Bob P.]

I installed a new power brake booster and master cylinder on my 66. The brakes have been bled. Now that I started the car and pushed the brake pedal, the pedal goes almost all the way to the floor. I have the push rod clevis in the top whole of the brake pedal lever. I have made some adjustments to the push rod, which hasn't seemed to help yet. Have I missed something? Should the clevis be mounted in the top hole of the brake pedal lever? What is the correct length of the push rod for power brakes? How far should I have to adjust the push rod into the booster? How do you know when you have the push rod properly adjusted? Thanks for your help!

[Bill M.]

Re: 66 Power Brake Issue

Should the clevis be mounted in the top hole of the brake pedal lever? What is the correct length of the push rod for power brakes? How far should I have to adjust the push rod into the booster? How do you know when you have the push rod properly adjusted? Thanks for your help!

Power brake pushrod goes in the bottom hole on the pedal.

Are you adjusting the booster-to-master puhrod? My '65 booster pushrod is not adjustable.

The pedal-to-booster pushrod should give you 1/16 to 1/4 inch free play from the pedal fully retracted position.

[Bob P.]

Re: 66 Power Brake Issue

Thanks for your help. I'm adjusting the push rod that is connected to the clevis that is attached to the brake pedal lever.

[Donald H.]

Re: 66 Power Brake Issue

Bob, did you solve your brake problem? I have a friend with similar issue. With the car not running, he had good firm brake pedal, but as soon as he starts the car, the pedal goes to the floor.

Thanks,

Don

[Don H.]

Re: 66 Power Brake Issue

I too am interested what he found. Please let us know. Thanks, Don H.

[Bob P.]

Re: 66 Power Brake Issue

Sorry it has taken me awhile to get back to you. I have adjusted the clevis to the point where there isn't much adjustment left. It has helped quite a bit, the pedal no longer goes to the floor. But these brakes certainly don't feel like what you would find in todays modern cars. It's been awhile since I did this and I don't recall if I also moved the rod to the bottom hole in the brake pedal lever or not. Will check tomorrow and let you know.

[Paul S.]

Re: 66 Power Brake Issue

I'm no brake system expert, but I did replace my entire brake system other than rotors (e.g., new brake lines, brake blocks, rubber hoses, MC and booster) on my 67 this Spring, as part of converting it from standard disk to power disk brakes.

The clevis definitely goes in the bottom hole of the brake pedal. On power brakes (when engine is off) properly bled and the clevis adjusted out (mine's out to the full extent of its travel), the pedal should stop at the pedal height indicated in the AIM, but when the engine's running, the pedal will travel further than is the case with a standard disk brake car. The pedal travel with standard disk brakes is not affected by the car running.

Feel wise, I can push the pedal to the full extent of its travel, when sitting dead stopped, engine running in drive (of my powerglide tranny), but it doesn't feel mushy and it doesn't sink easily to the end of the pedal travel. Car stops on a dime with the pedal well off the floor, including threshold braking from 70+ MPH to zero. Overall, I wish I had done the power brake conversion 3 years ago when I first bought the car and had to replace the MC. I was never satisfied with the braking until I completed the power brake conversion with all new parts.

If your brake pedal drops to the floor before you've even gotten it on the ground/on the road, to me that means either you have a MC that's bad or has the incorrect push rod in it (not an issue with a 67 because the MC is the same for power and non-power brake cars), has not been properly bled, or the brake system has not been properly bled/is pumping air in from somewhere.

Also, if you're using DOT 5 brake fluid, the pedal may feel a bit softer (I've had both DOT 4 and DOT 5, and cannot honestly say that the end result was significantly softer on DOT 5 brake fluid).

[Bob P.]

Re: 66 Power Brake Issue

I checked the car earlier today to see what hole the push rod is in and it is in the lower hole on the brake pedal lever. Hope this helps!