Packard Forum Index » V-8 (1955-56)

I believe one or two might have used a Hydro-boost kit but don't remember reading any feedback on how it was mounted and how well it works. If it was mounted low like the Electro-boost it might be a less expensive option to keep the pedal look stock. Since it relies on the engine running I would still have the same questions on the 1:1 pedal ratio and reserve capacity to stop the car if the engine quits. One kit I looked at has a preferred ratio of 6 or 7:1 which is as high as a manual system. The engine stalling scenario seems much more likely to happen than losing electric power on the Electro-boost so a concern.

A 52-55 arm is on the passenger side of steering column so too much interference to mount anything high on that side and brackets and arm is too far away from vent area to make modifying that arm feasible.

If you had a 56 pedal setup in which the arm passes right in front of the air vent and no factory AC, it might be a simple matter to mount the hydro or electro boost in the vent area and modify the pedal arm for a higher take off point to increase the ratio. Not knowing exactly what all the different hydro-boost system require makes it just speculation if one would work. My car has factory AC and a very confined space. I played around with a revised 56 arm and some redirected linkage in the vent area when mounting a modern vacuum booster and cylinder. It is mounted somewhat vertically & angled toward the engine. It works and has an approx 3:1 ratio but is not fully optimized and that ratio is marginal. Like most of my projects, got tired of playing and moved on to something else before I was totally happy with the feel. One of these days I might redo, revise or refine that a little more but leaning more toward getting a smaller unit like the electro boost. With the higher ratio of even 3:1 would feel much more comfortable using that one.

If either hydro or electro boost can be mounted normally or horizontally in the vent area it might even be possible to disguise the engine compt side with an easily removable but fake vent tube like setup that at a glance looks stock from the top. Have the best of both -- stock looks on the pedal and in the engine cmpt. Just wish that was possible with the factory AC car.

I sent a tech question about the HydroBoost as a retrofit for the Packard to Summit They had no answer and referred me to the manufacturer. I will do that next week.
The units with master cylinders are posted on eBay for around $650 or less. The lines are listed at around $250. I think the units could be picked up at salvage yards for much less.
The unit seems to be designed similar to the original BTV with the brake pedal functioning to activate the unit and not the master cylinder. The new units seem compact to fit in the limited space.
I am uncertain whether the units share boost with the power steering or require a separate pump....and also unsure if the old pump has enough boost to handle both.
I appreciate your concern about reserve capacity if the engine shut off or there was electrical failure with the ElectroBoost. To some degree the ElectroBoost site asserts that there is a reserve of up to 20 pumps if the electricity failed and manual brakes would still work.
I have not heard whether the ElectoBoost will work with the 12 v positive ground system.
I would prefer a dual master cylinder to mitigate the risk of brake failure from more common issues of line or wheel cylinder failure, but the recent episode with the Cadillac HydroVac sucking the brake fluid into the engine and sudden brake failure has prompted my inquiries.
If anyone seeing the posts has installed either system and maintained the drum brakes and original pedal, I would hope they,would respond.

Sorry to hear about your brake failure in the Cad. It must have been a very stressful experience by your urgent need to make a replacement. It seems others feel the same way about the btv. I have not had such an experience but always drive the clipper with more space and slower speeds.

As someone who has driven and serviced hundreds of cars and lt trucks I can make a few statements on the hydro boost sys used thru the 90s up to 2001. The units as used in most astro vans and gm c lt trk /vans are extremely durable. I recc you check the output pressure of the gm pump as compared to the packard unit used with the stock assist ram to see if the pressure output is the same or you may have reduced assist.

Those units were engineered to be as bullet proof as the gm vac boosted masters (70 n up) And the fact that I do not recall changing one for a failure or any coworkers ever replacing 1 speaks volumes. sm seepage or a mist from hoses was all.As far as pedal feel and reserve on stall- my experience was the hydro boost had a slightly "firmer" pedal feel on the first 1-2 inch pedal travel on"a quick apply"(quick apply not panic apply) and a slightly spongier feel at the bottom of the travel as compared to a vac asst sys. Just ask a friend or aquaintence to drive their chev or gmc astro to Feel for yourself so ensure you will be satisfied. These are easy to spot as under the hood there is a smaller black unit with 2 hyd hoses running to it rather than a lg round vac can with 1 vac line. The fist size gold anodized can mounted on the unit is I believe an accumulator and on an abandoned road or other safe area you may turn the ignition off 1 click (to stall engine and not all way to lock as this will lock st wheel) and test for 1 brake apply reserve. Lets all be honest- upon a stall cond you have verv heavy steering and are pulling to the roadside so 1 assisted stop can be assumed to comply with safety req? Lets face it, 5,10 or more pedal applies is this really nec real world. Any thoughts? I would be interested on your experience if you go this route and these units are likely a dime a dozen. Would you like me to check my factory lit to get some pressure and vul specs of the gm remote pump? may be avail on a google search as well

Would you like me to check my factory lit to get some pressure and vul specs of the gm remote pump? may be avail on a google search as well

Would your specs have any info on the pedal ratio recommended or required for the HydroBoost? Most GM applications seem to have a fairly high ratio for their brakes -- even on the BTVs. While Packard mounted them low and used 1:1 the mid 50s Chevys that used the BTV had them mounted high on the firewall with a higher pedal ratio.

And 1 more thing. There is a very slight "hiss or whine" from the system on a hard brake pedal apply. Think gm p st hiss like when the st wheel is turned and held on the st stop but not as severe.

For what it's worth, Packard pressure specs on PS pumps are 550-800psi on Bendix unit pumps and 650-900psi on pumps used with Monroe units.

Oh thanks howard for the remind. I wanted to add I believe the pedal was a hanging pedal as most of the vac asst and the pedal would be a 5-1 or 6-1 ratio. This would need to be verified and maintained. Can someone who owns 1 take a look and verify ? This will not be in my lit of factory specs of the pressure system but there are guide lines on pedal ratios. Upon engineering hot rods in the past i came accross the needed ratios. May i post them here for others?

I think it is important for all those who are mod,retro, classics or designing hot rods or customs know the specs, back round and basics first.