Re: 1954 Pacific disc brake conversion kit

Posted by HH56 On 2020/8/24 14:18:47

It appears someone has done a good job of documenting the steps involved so adding discs mechanically is apparently fairly painless providing the proper kit is used. Having never done it I cannot comment on the precise order but it seems reasonable. Be aware that 54 was a transition year for Packard and particularly the Clippers inasmuch as the small wheelbase models had some suspension and brake configurations that did not necessarily follow what was done on other years similar models. Just be sure of what was used on your model to ensure buying the correct kit. The xxx kit that a vendor says fits all years of such and such model may not hold for 54.

From almost every site I checked, discs typically need more pressure and take more fluid volume than drums and cannot use a residual valve without having the discs drag. That is something that needs to be checked because if the kit you use needs the increased volume, in my opinion using the Bendix power brake master is more of an issue because of the way it works and the volume of fluid out it can deliver. I know it has been done and people report no issues but I wonder how much of any safety reserve has been used up. Is there enough pedal travel left for a safety margin to allow for any wear or mis-adjustment at the pads or shoes. It is sort of like the issue I have with those who have used the Electro-boost systems to replace the Bendix TreadleVacs to keep the unit in the same locations and pedals unchanged. In those installs they have compensated for the lack of the appropriate pedal ratio by increasing the boost on the electric unit. What happens if a power component fails and suddenly there is no boost or reserve available.

My concern with the Bendix power brake master is that it does not have a piston pushing a volume of fluid in front of it like a manual cylinder or modern masters but rather uses a solid steel cylinder that slides into a volume of fluid to displace an amount to the wheels. To get any increased volume to the wheels for discs the pedal travel needs to move the rod farther into the master. The question is with more pedal travel, at what point does the pedal travel reach its limit and can deliver no more. Add to that, if the vacuum portion fails -- even with self energizing drums all around -- because of the 1:1 pedal ratio the car is an absolute nightmare to stop when going at any decent speed -- almost to the point of having soiled upholstery. I can tell you from personal experience, if going up a hill and the engine stops and you start rolling backwards, it is much worse because there is no self energizing of the shoes thus no brakes period. I would wonder if having enough pressure for discs under no vacuum conditions would be even more of a challenge.

Assuming the TreadleVac could be used safely then that leaves the residual valve. I believe that obstacle could be overcome by removing the existing valve from the output port of the master and reusing the original brass block and ports for lines out. Some new tubing and careful bending could add an inline combo proportioning and residual valve adjacent to the booster in the portion of line going to the rear wheels only.

Master Power Brakes site has a good FAQ that goes into the use of existing masters rather well but there is no mention of the Bendix units since they are so old.