Packard Forum Index » V-8 (1955-56)

The PS pump pressures given earlier were taken from 55 Service Counselor Vol 29 #4 so should be accurate. Packard suggested not to interchange pumps as erratic steering and noisy pumps could result. If you have the Bendix steering and want to use the original pump, expect you might be limited to the lower pressure to use with the booster unit.

Here is an illustration showing the BTV location utilizing the 1:1 ratio. Another of the plumbing that might be helpful. There may be an official drawing somewhere but for practical purposes, from the floorboard opening it is a 6 x 6 x 11 1/2" long cylindrical unit. The rod from unit to pedal is approx 5" long. The May 52 Service Counselor Vol 26 #5 has a few photos of the first original units with the external air vent. Yours is the same except the later air vent setup is built into the top of canister instead of being separately connected by a hose. Both counselors are available for download in the lit section.

If the new unit will fit the existing space, plumbing is not too much an issue on V8s. If lines are in good condition, since there are separate lines to front and rear wheels you may be able to just reuse the existing lines by disconnecting them from the single outlet fitting and transferring to the new dual cylinder unit ports. At the worst, if the ports are in very different positions or another size, an adapter or different length of tubing for the front line to the front junction block and a short extension and coupling for the rear might be needed. V8s use standard 3/16 tubing and fittings available at most parts stores and the brake light switch is in the front juntion block so nothing to be changed there. Depending on the new unit it may or may not have built in residual valves. You should have those just to keep a slight bit of pressure in the wheel cylinders. If valves are not built into the new master, they should be added inline. That is one thing to verify with the rep as to need.

The other thing I still would like to hear officially is what happens with 1:1 ratio if the reserve is out. At the most with direct foot pressure you can only put maybe 100 to 150psi to the pedal and cylinder. Is that enough to stop the car with no reserve. A good example of no reserve is what happens if you had to coast your way off the road tapping the pedal a few times or when the car has been sitting a long time and the engine hasn't been started to build or maintain power in the accumulator. Will there be brakes with that low a ratio if you had to nurse the car off the road or went to push or tow the car after stalling.

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In any correspondence be sure to indicate 4 wheel DRUM brakes. NO disk.
55 and 56 front are 1-1/8 wheel cyl.
55 and 56 rear cyl range from 1" to 1-1/16."

For ease of communicatio just use 1-1/8 front and a plain 1" rear.
1/16" is negligable.

I looked at the photos of the unit and instructions for installing the CP3100r. Don't know why some companies are so reluctant to give dimensions. I would guess the unit is approx 4-5 inches square plus the length of a master which would place it in the neighborhood of BTV length.. Price wise, not sure it would save much over an electroboost. By the time you buy a master cyl plus whatever is needed for the brake and power hydraulic lines it will be fairly close.

I like how the first line in the instructions is the obligatory CYA statement of "the system is intended for off road use only". The install doesn't sound too terrible but it is general so they really don't give much detail. Don't remember what fitting the Bendix pump uses but hopefully adapters are readily available to convert from Bendix port out and supply the needed original style steering port plus supply the AN-6 style the unit requires. Another thing is they specifically say power steering fluid and not ATF. That shouldn't be too much a problem other than bleeding all the old existing Packard ATF out of the steering mechanism. The rod clevis they supply is the typical hole thru the GM arm type so something will have to be found or adapted for the Packard pedal attachment.

It does appear to be physically smaller than a vacuum setup so definitely worth looking into but not sure it will be much better, cheaper or easier than the electroboost.

HH56.
U indicate the double diaaghram power unit u're using now causes extremely sensitive brakes. Is it possible to move the current dual diaghram powerunit and mc to the old BTV space that is now setting empty and therefore retain the oem stock 56 brake pedal.

LEt me put it another way:
If your current set up is so sensitive theen it mite very well lend itself to the 1:1 stock pedal ratio?????

If it happens to be too long then a single line mc should be a good bit shorter.

Keith, I would be very reluctant to use 1:1 because of the possible loss of boost issue. Even at 3:1, running at slow speed with no vacuum as a test the brakes were marginal and took a distance. Granted, I wasn't standing on them but it was still not something I would want to take a chance on.

Howard- Thanks for the diagrams. The email received from CP sounds promising. The unit appears to be apx the same size as the BTV. Overall length with master cylinder is supposed to be 16-16.5". The width is 4.5" with a 2" accumulator making overall width 6.5" with widest point being at 2 and 7PM positions.. The unit can be mounted at any angle- even upside down for clearance.
The email recommends a 1 1/8" master cylinder bore rather than the 1" I suggested since the smaller bore may make the unit too touchy since the boost is purportedly 100-200% greater than the BTV.
There was a unit listed on eBay today for $498.75 and a Wilwood master cylinder w 1 1/8 bore and remote reservoir was listed at $64.99.
The email asserts that the 1-1 ratio is not a concern due to the accumulator.
I will check on the pressure needed and whether the current Power steering unit can be adapted to operate both. I will ask specific info on stopping ability w 1-1 ratio if engine or hydraulic pressure loss occurs.
In a way I assume we have a similar problem with the BTV coupled with the inherent concern with a single line master cylinder.
A bit tied up this week but I will try to get answers and keep all posted.
Thanks to all for the support info.
Stay well
RJR

Sounds interesting and will await more details. One other thing that I think needs research or more info is the total length.

If that 16" figure is accurate then depending on exactly where or how the unit sits, there may be an issue. The BTV is laid out essentially in a straight line with master directly in line with the pedal. If planning on using the same space and mounting plate, if the hydro is laid out the same way I believe it will be too long for the space. The steering column and box sits directly in front of the roughly 12" BTV unit with maybe an inch or so clearance.

yes. Most interesting.
As for the length of the GM unit keep in mind that the OEM BTV has less than 1/8" FRAME clearence at the forward most point of the BTV mc. Somewhere a few years ago i posted a pic of the BTV fitted to a 56 Exec with fender removed that shows how close the BTV mc sets to the frame.

IIRC the frame has an indention in it to accomodate the BTV. So if the GM unit is longer that mite present another obstacle to overcome.

I spoke to the CP rep today. Long story short- it is not going to work. His initial assessment and sizing were quickly revised when I directed him to the Forum and diagrams. His unit is 16- 16.5".... Without the rod which would cause interference with the frame. He was a bit taken back by the diagram and the 1-1 arrangement. He didn't think the pump would work...and the master cylinder has to be level ....etc, etc.
Pretty much a waste of time.
I will keep looking.
By the way- the unit does not afford several pumps before putting you into the ditch. You would be trying to stop with a conventional brake attached to the original pedal.
Sorry if I got anyone's hopes up...but this is a bust.

Sorry to hear that. Your disappointment is understandable. I am feeling like all would be better served if the final resolution used over the counter, readily available parts with million mile proven track records.
Seems there are many blogs on the web of vac to hd retro and some seem to show a HIGHER pedal ratio and some say a pump upgrade is required and some use the factory vac boost pedal assm and the original pump. I have also found there are different accumulators(gold,silver,blue) with differing pressures and pass car,3/4 ton, 1 ton models with different boosts. Too many variables and the fact that even with moving the unit up and pedal down slightly the best pedal ratio to be achieved is 2 to 1 it seems unlikely to be an answer to all concerns.