Packard Forum Index » V-8 (1955-56)

I know there has been many a discussion about the treadle vac unit, however the search function is not working for me today, giving a fatal error.

My treadle vac failed while driving a few years back, just around the time I had learned of other people's units doing the same.

Long story short, no one was hurt and the patrician wasn't damaged.
However the car was drivin home, and the treadle vac was removed.
That's how it has sat for the past few years.

I have checked out the Panther project, and a couple of the other conversions done, and am starting to plan mine.

I understand the pedal ratio needing to change and size limitations on swapping a new unit in.

I'm currently looking at a BTV Replacement offered by ABS Power Brake, page 12 of their catalog, designed for the Chevys. However it's recommending a 6:1 ratio and have not heard back from abs about the mounting bolt spacing or the piston size. If this unit is generally the same dimensions as the BTV would I be safe to say the master cylinder will clear the steering colum, or am I still looking at a remote fill reservoir?

I'm curious if anyone has tried anything new since those conversions, and more specifically if anyone could foresee any fitment issues with one of the Chevy "treadle vac replacements" offered by abs power brake or one of the other vendors.

I'm sure it will get asked, but I have not yet dissasembled the BTV, however the MC has some crusty stuff in it, and right after the failure the MC was almost completely empty and had been checked and filled before my 30-50 mile drive. The BTV has sat on the shelf since removed.

There have been many threads for sure on this. Can post links to some if you want to read through them. There is alot of good info. The pedal ratio seems to be the issue and limiting factor and as many have stated, pose an issue upon engine stall and loss of assist. You need to do your homework to make your mind up.

Hey thanks for the response, links would be great, as I don't know if it's my computer or the site acting up but I'm still getting the fatal error wen searching.

Also I assume there is no dual master that will bolt up to the BTV booster, without some sort of adapter plate.

Brakes are something I know little about other than swapping in and out stock stuff, but I have learned a lot from you guys on the forum, and the various BTV threads.

The BTV replacement won't work as a direct replacement because Chevy mounted their unit up high on the firewall and was able to get a decent ratio from the start. The modern replacement unit sold for Chevy use can bolt in because of that location. Packard mounted low and suspended the pedal differently so no decent ratio is possible with stock components and location.

One solution might be to investigate the air vent location. If authenticity is not a factor that is a very good option. Here is a thread with some instructions and components for that approach.packardinfo.com/xoops/html/modules/newbb ... rum=12&post_id=27924#forumpost27924 The other relatively easy option is keep the original location which Craig detailed using his pedal mods.

The other and by far most expensive option is to use the ElectroBoost system from ABS. Several have gone that route and mounted in the original location using original pedal. The main concern with that one might be what happens if the power unit fails or accumulator is depleted since it will revert back to 1:1 and might not be able stop the car.

My plan for the pedal ratio as long as I'm not missing something is to build a bracket/lever on the back of the stock pedal closer to the hinge point that drops down the back of the pedal to connect the boosters push rod. Kind of trying to hide it in the pedal arms recess.

However I'm not too sure if the Chevy unit is close to the same dimensions, and the suppliers don't seem like they want to give up too much info on them, at least over the web.

I would of course like to keep my Patrician as factory as possible.

I checked out the electroboost and like the looks of it, just want to solidify my plan before I go ahead and spend the cash.

Don't mean to be a bugger and ask the same old questions over again.

The steering column prevents much change in location upward so you will have to move it to the side to go higher. The steering box limits the length of the unit you can place in the original location. A single diaphragm 7 or 7 1/2" booster plus the dual master is about it. A dual diaphragm booster has to tilt off to the side to miss the box but then you start running into other problems.

Not quite following your approach on the ratio change. The higher take off is good but then you have the issue of height and angle on the booster. The rod has to be in a fairly straight line so not sure how that will work with the column. I've tried several rube goldberg arrangements from levers to bellcranks and using the stock pedal as is is almost impossible because of space limitations.

It would probably help to have some sort of drawing on hand, but trying to clarify, moving down an inch or two on the pedal from the hinge point, back side, welding in a rod vertically at a yet undetermined angle, to the pedal running down to the booster rod. Almost leaving the stock pedal there just for looks.

Reading the link you provided, I discovered I had posted in that particular thread, and it looks like my unit failed sometime in 2007. Thought I don't believe it was the vacuum leak I had originally thought it was. So it looks like I've been awol and had my car sitting for the past seven years not realizing it. No wonder I've been itching to drive it.

Wow. sitting for that long. Time does fly. There may be other things on the car needing attention. I read the threads earlier and looked at retroing a hydro with a FLAT plate and a raised attachment point but some simple rough drawings and calculations wont get better than a 2 to 1 ratio. I dont believe fancy pedal arrangements are the answer- KISS for safety on brake systems You may be better served to get a reblt btv and flush and bleed the whole system to get you up and running to shake her down and see what else needs attn to be driving by spring. Portland Oregon is it? I could have designed a hydroboost syst to work with the proper assist and little mods to the car with a flat plate so as to be able to go back factory easily but others concerns of ratio and engine stall with stopping power upon failure would not be fully addressed. Wondering if even thats a moot point cause if hydro assisted in a gear-start Ultramatic is utilized could one ever loose assist? on engine stall could one just go to low gear and spin the engine thru the trans with rear pump gear start and still have assist? even with a dead engine? Seems addressing every ones wants and concerns incl A/C cars is a tall order.

If your not using the btv for sure and you were closer to me I would pay the shipping to me if you would donate it.

1. THe OEM 55-56 packard pedal is too weak to accomodate any modification
to a hifger pedal ratio. SPECIFICALLY the way it is hinged at the fire wall.

2. An increased pedal ratio will require a firewall to dash support. Otherwise the sheet metal firewall will flex too much and crack.

3. Useing SPECIALTY aftermarket parts usually results in a futurre lack of availaability of replacement parts. About 5 to 8 yrears.

TO retain the oem power unit with a retro fit MC would be a good trick. THe MC will have to be approx 5/8 bore MC. Findding such an MC an even better trick especialy with enuf stroke equal to the oeem BTV MC.

Anyone want to do some machiineing??? THen modify the oem BTV MC to use somekind of reaadily availaable rebuild kit such as maybe 80's honda ciivic (13/16 bore a bit too big). Good luck. Keep us posted.