1967 Manual brakes

[John C.]

I recently purchased a very original 1967 L79 with an aftermarket power brake master and booster. Being a numbers matching factory original guy and this being the only item not original to the car, I purchased a DC coded master cylinder and removed the aftermarket one along with the booster. I also replaced the brake pads, checked the condition of the rotors and completely bled the system with DOT 4 fluid. I was very surprised to see how poor the braking is on the car. I do not believe that I can lock the brakes given how much pedal pressure I need to apply just to get the car to slow down. Am wondering if this is normal? Any input to this thread is welcome and appreciated.

[Leif A.]

Re: 1967 Manual brakes

John,
Did you bench bleed the new master cylinder? It sounds like there is air in the system. As simplistic as these brake systems are, they can be a bit cantankerous when it comes to bleeding the system. I, also, have a '67 L79 with factory power brakes and I can assure you they work every bit as good as a modern power braking system.

[Mark F.]

Re: 1967 Manual brakes

John...I, also, have a '67 L79 with factory power brakes and I can assure you they work every bit as good as a modern power braking system.

John,

I agree with Leif.
I have factory PBs on my '67 L-68 and they work like a charm even after 20+ years post re-build; bench bleed and gravity bleed.

[Donald H.]

[Mark F.]

Re: 1967 Manual brakes

I may be wrong

Don,
No you're not wrong.
Glad to hear the same applies to non-power.
Best brakes I've ever had on a car that was made before 1967 !

that's including my 1938 Ford coupe w/ CABLE brakes! - Absolute WORST brakes ever ! several times I had both feet pushing down on the brake pedal (one on top of the other) - and both hands grabbing the underside of the metal dash (yes I left go of the steering wheel) - and still barely came to a stop inches away from a car that stopped suddenly in front of me !

[Rocco S.]

Re: 1967 Manual brakes

I agree with Don. I too have a 1967, L79 non-power brake car. I replaced the original MC with a GM exact reproduction unit and calibers with Lone Star S/S sleeved, "O-ring" calibers and the system has been perfect. I bench bled the MC, used a Mity-Vac starting at the right rear wheel and moved forward. Finally, finished with the traditional pump, pump, pump and hold at each wheel. That was over 5 years ago and brakes are still excellent. Albeit, they need a little more foot effort since they are not power.

[Donald H.]

Re: 1967 Manual brakes

I had a 66 with power brakes and mostly the difference between it and 67 with non-power brakes was the pedal pressure needed. The 67 will stop on a dime and the 66 would stop on a dime and give you some changes!!

Don

[Joe L.]

Re: 1967 Manual brakes

Don,

that's including my 1938 Ford coupe w/ CABLE brakes! - Absolute WORST brakes ever !

Mark------


The automotive industry did not universally go to hydraulic brakes because cable-operated brakes worked just as well.

[Keith B.]

Re: 1967 Manual brakes

in 67 both standard brakes and power brakes used the same master cylinder. and when both are up to OEM specs they both should lock up the wheels.

[Mark F.]

Re: 1967 Manual brakes

Mark------The automotive industry did not universally go to hydraulic brakes because cable-operated brakes worked just as well.

Hi Joe,

Yes and Mr. Ford was one of the last to switch over in 1939.

The problem I had with cable brakes (unlike solid rod versions on Model As - I had one of them, too) was they stretched.

Cable shorteners were illegal for Pennsylvania's twice-a-year inspections back then (early '70s), but even with "new" cables it was almost impossible to keep them (at least mine) in good adjustment w/o them. Even w/ a flathead 85hp V-8, the car only weighed ~2,600 lbs. - a lot less than a C2 Vette. Those were the days, eh ?

1938 & 1930 Fords TDB.jpg

[Duke W.]

Re: 1967 Manual brakes

I recently purchased a very original 1967 L79 with an aftermarket power brake master and booster. Being a numbers matching factory original guy and this being the only item not original to the car, I purchased a DC coded master cylinder and removed the aftermarket one along with the booster. I also replaced the brake pads, checked the condition of the rotors and completely bled the system with DOT 4 fluid. I was very surprised to see how poor the braking is on the car. I do not believe that I can lock the brakes given how much pedal pressure I need to apply just to get the car to slow down. Am wondering if this is normal? Any input to this thread is welcome and appreciated.

This is a common issue. In a 1965 SAE paper it was stated that Chevrolet decided to not include a vacuum booster in the new disk brake system as a cost saving measure, and they established a design criterion that a 1g deceleration rate require 120 pounds of pedal force. Of course, OE tires of the era would at best, on an ideal surface, generate no more about 0.9g.

All modern cars have power brakes and a 1g stop requires on the order of 25-40 pounds of pedal force.

Twenty-twenty hindsight tells us that Chevrolet's cost saving measure was ill-advised, but, remember, in the mid-sixties, a lot of older cars did not have power brakes, so drivers were accustomed to higher brake pedal force than today.

The same can be said about the steering. We've become accustomed to power brakes and steering for 40-50 years, so getting into any old car with no power assist can make it steer like a "truck" and have "no brakes".

The solution is either get used to it, spend more time in the gym doing squats with weight and pull-ups, or "upgrade" to power assist.

Duke

[John C.]

Re: 1967 Manual brakes

Leif, Thank you for response, yes I did bench bleed the master. I do get a good pedal, just not a very good stopping power. I surely cannot lock up the brakes. Would you say that even with a good pedal there could be air in the lines?

[Joe L.]

Re: 1967 Manual brakes

Leif, Thank you for response, yes I did bench bleed the master. I do get a good pedal, just not a very good stopping power. I surely cannot lock up the brakes. Would you say that even with a good pedal there could be air in the lines?

John------


Yes!

[Joe L.]

Re: 1967 Manual brakes

This is a common issue. In a 1965 SAE paper it was stated that Chevrolet decided to not include a vacuum booster in the new disk brake system as a cost saving measure, and they established a design criterion that a 1g deceleration rate require 120 pounds of pedal force. Of course, OE tires of the era would at best, on an ideal surface, generate no more about 0.9g.

All modern cars have power brakes and a 1g stop requires on the order of 25-40 pounds of pedal force.

Twenty-twenty hindsight tells us that Chevrolet's cost saving measure was ill-advised, but, remember, in the mid-sixties, a lot of older cars did not have power brakes, so drivers were accustomed to higher brake pedal force than today.

The same can be said about the steering. We've become accustomed to power brakes and steering for 40-50 years, so getting into any old car with no power assist can make it steer like a "truck" and have "no brakes".

The solution is either get used to it, spend more time in the gym doing squats with weight and pull-ups, or "upgrade" to power assist.

Duke

Duke------

I ordered my original owner 1969 with standard, non-power brakes. In 1973 my brother bought a new 1973 Corvette. This car had power brakes. I drove it a few times. I could not discern any braking difference between the two cars.

[John C.]

Re: 1967 Manual brakes

Hello Don, Thank you for responding, as I stated in the original thread, I removed the aftermarket power brake master and booster and can say that the braking was not so great with the power system installed. Seems like there is something else going on here. Would you know if the proportioning valve would cause poor braking if defective?