Packard Forum Index » Post-War (1946-54)

Hello,
Anyone have the power steering pump specifications? My service manual doesn't. I'm looking for gpm, max pressure/relief valve pressure and minimum pressure. The manual only states the pump should have at least 650 psi.

I'm looking into converting the treadle vac to hydroboost, provided the power steering pump will generate the pressure and flow it needs.


Thanks
Earl

Packard did not as a rule provide much in detailed pressure specs and when they did it was often in a fairly wide range. On page 4 and 5 of the Power Steering Training Manual they give a bit of info on how the pump and valve operates but for specs, info is probably the same as the service manual and just says the pressure depends on how much resistance is felt at the wheels and relief valve will work if pressure exceeds 650 psi.

55-6 models used a similar design pump but had two different steering systems so pumps had different relief valves. On those the range as given in the April 55 Service Counselor is 550-800 for pumps used with Bendix systems and 650-900 for Monroe systems.

During all normal driving the pressure in the PS system is very low as the fluid merely circulates until assisted steering action is called for. The system will only approach 650 psi when yanking the wheel out of a deep rut or some such and the pump essentially dead heads against the power cylinder piston. Its a little hard to see how a hydroboost can share with that. Hit the brakes on a straight stop and there is almost nothing for the hydroboost to work with as it is all bypassing through the steering control valve.

Quote:

Thanks! I haven't seen that publication. Way more information than in the service manual. As you stated the relief valve is 650 psi. The training guide states 1.4 gpm. Unfortunately the pressure and gpm is half of the needed requirements of a hydroboost. So back to looking at vacuum boosters. I don't believe I want to upgrade the pump or run a second pump.


Thanks,
Earl

Quote:

Thanks! I appreciate your reply! I believe that to hold true of all hydraulic systems. Once you load the hydroboost by pushing on the brake pedal, pressure would increase as you're working the pump with restriction. The hydroboost is first in the circuit. But unfortunately the Packard pump is half the gpm and pressure needed for a hydroboost. I prefer hydro over vacuum and they are psychically smaller, making it easier to install in tight areas. Plan B, seeing how big of a vac booster I can fit. Likely using the crotch vent opening.

Any thoughts on the strength of the factory PB pedal pivot mount? To get a 4.1 ratio I need the booster rod hole to be 2.3" down from the pedal pivot. That will add a lot of leverage to the pivot.


Thanks,
Earl

Those that have added a vacuum booster in the stock location had to modify the pedal which changes the location of the pedal pad in relation to the accelerator pedal and is very noticeable inside the car. The stock 52-55 pedal arm is on the right of the steering column so not much space to mount a booster up higher because of interference on the engine side.

The 56 pedal arm straddles the vent opening to the left of steering column and several have taken advantage of the vent opening to mount the booster. You do sacrifice the air vent but most feel it was an acceptable tradeoff. I believe all who have done this have used a different pedal with a mount location higher on the firewall. Some pedals have been from other mfgs cars and I believe one or two have used aftermarket universal hanging pedals. Those come with the takeoff point higher on the arm. Most used the pedals as shipped but one or two have modified the arms and stock pedal so as to weld on the original Packard pad setup. That way they still have a mostly stock pedal look and a location in the approximate area Packard placed them.

It might be possible but don't know if anyone has tried under the floor. Was an idea thrown around but doubt the frame depth is deep enough unless an aftermarket pedal and a booster setup can be fabricated so booster is positioned farther away and enough back so it could fit into an area under the seat. That way a piece of floor could be cut out and boxed in so booster top could be raised up slightly above the frame. Obviously a remote fill setup would be a must.

If something like an underfloor booster was tried I had toyed around with how to keep the pedal look stock. Still think it would be possible to have an aftermarket floor pedal come up using the original location the Treadlevac rod met the pedal and cover it with a longer bellows. Make some kind of roller and link arrangement to fasten the underfloor arm to the suspended pedal to allow for different or a sliding motion since the arcs would not be the same.

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Correct my 53 pedal mounts to the right of the column but swings over by the crotch vent. Looks like I can keep the original pedal set-up and mounting the booster through the vent opening, maybe notching it a bit. Eyeballing it, it looks like it would link up with the pedal. But the pedal pivot may not be up for the 4:1 leverage. But that was going with a hydroboost unit. Vac booster is much larger. Would have get dimensions of a dual 9" booster to see what fitment is like on the engine side.

I would use the crotch vent or go higher. I would not try the stock location. To get pedal ratio your pedal would be on the floor dragging.

Another option is get a manual brake frame pedal assembly and just go with a manual dual circuit master like I did on my 52 Dodge Coronet. The Packard is 3spd manual, so it already has a frame mounted clutch pedal. But don't know what's involved in sourcing the parts and installing them. I highly doubt a dual 8 or 9" vac booster would fit under the floor.

Note, I will also be putting disc on the front. Goal is to make it as safe and reliable as I can for modern interstate driving.


Thanks,
Earl

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Not sure you would need a large 9" booster. Craig used a single 7 in the stock location on his 55 when he developed the first conversion but that required some serious pedal mods. He said the new pedal location was OK after getting used to it but I think it is too low and close to the floor for my likes. There is a dual 7" booster that works well and fits the vent space reasonably well. It might even be possible to mount that size booster under the floor if the top could get above the frame by an inch or so. Master Power Brakes is where most have bought their components and they have helped people put together viable combinations. ABS Power Brake also has universal street rod applications.

Your diagram is interesting. But I don't know if the original pedal would travel enough. Be like a bellcrank. I seen a Packard with a hydroboost below the floor using the original pedal with a bellcrank to actuate the hydroboost. It was a YouTube video and didn't go into details or show it closely.

https://youtu.be/Wh9CsbrDkN0?si=znDtzLyhKGFQm6mc


Earl

Can't use a single booster on disc/drum or disc/disc. You need a dual booster and likely 9" to generate the master cylinder psi for disc. Drum/drum doesn't require much pressure and you can use single smaller boosters. Might get away with a 7 or 8" dual booster if you don't mind more pedal effort and depending on vehicle weight.

I agree. I wouldn't want the booster in the original location. I like my brake pedal up off the floor.



Earl