stingry

For those who have seen my other posts.

I am retrofitting a vaccum Power Booster in to my 1970. I purchased a re-manufactured booster and M/C from a local autoshop. (they will refund the dollars back if they don't get one)

The shaft connecting the Power Booster to my brake pedal is 4 inches long. It needs to be 5-5&1/2 inches long to properly connect to the brake pedal and operate the rear brake light switch. (The length changed in 1977).

PHOENIX had a similar problem and found a supplier and part number for the correct power booster. I tried a search on the forum but had no joy.

DOES ANYONE have the part number for a correct booster?

Thanks in advance.

:cheers:
Pete


[Modified by stingry, 1:31 PM 1/29/2004]


[Modified by stingry, 1:31 PM 1/29/2004]


[Modified by stingry, 10:12 AM 2/3/2004]

comp

no help ,just a bump up :cool:

stingry

Anyone?

If I don't get a correct booster soon I may need to cut a hole in the floor and stop FLINSTONES style.

Thanks,

Pete

Van Steel

Pete
are you sure you got the correct PB or MC. My PB & MC work fine together and my pushrod is not 4" or 5" long. I think you MC is incorrect.

69ttop502

Stingry, I just converted from power to manual brakes on my 69 and my booster is for sale if you want it. It worked fine when I pulled it off. The rod comes with it. Bill.

ettev

Are you certain you have the booster mounted in the correct location on the firewall? What exactly did you do to modify the floor pan to gain additional leg room? The power boosters changed design in 1977, so you should have the correct setup. Keep in mind that with power brakes, once the clevis is connected to the brake pedal, the pedal will be closer to the floor pan than it was with non-power brakes. Probably by an inch or so. Also, your stop light switch is adjustable at 2 locations. One where it's mounting bracket attaches to the main housing/brace, and at the switch itself via the nylon threaded end where the switch passes thru the mounting bracket. The two mounting bracket bolts are up high and REALLY fun to get to unless you have either your steering column or drivers side dash out (or both). Worst case, hook up the brakes and see if they work correctly with the setup you currently have. Then worry about the stop light switch. You can always "extend" the paddle that presses in on the brake light switch if need be by JB Welding some pennies or the like to the face. It's gypsy, but it might solve your problem.

stingry

Dan, ettev, bill,

Thanks for your input. Here is where I am at. I am about to do a tech article on this as it has been so complicated!

First of all thanks to all the guys who suffered before. I share your pain but have learnt a lot through the forum archives:

BOOSTER
I have either purchased or ordered in 5 BOOSTERs. They are all remanufactured by CARDONE. the part numbers are:

50-1200 Booster only for 68-76
54-91200 Booster and M/C for 68-82 (will work for both as M/C matched to booster)
54-81200 Booster only for 77-82

There were several design differences between them but mainly cosmetic. The main difference is that the 77-82 booster has a SHORTER pushrod going into the Master Cylinder as the 77-82 has a shallower hole. The 68-76 Booster has a longer rod going from the booster the MC as it has a deeper hole. You need to make sure that in either case you get a PB Master Cylinder, it has a larger bore and hence more pressure.

Almost all boosters have the same length of rod coimg out in the BRAKE PEDAL/FIREWALL side. This is the side which is connected to the booster diaphram and is NOT adjustable in length. Some rods had more thread then others which may allow for MINOR adjustment at the clevis that attaches to the brake pedal. The length of this rod ie from firewall to end is approx 4 inches. I have seen variations +/- 1/4 inch. this rod will either need to be extended by using some threaded hex stock or the clevis will need to be lengthened to meet the rod.

PEDAL ASSEMBLY
Whilst the large hole that the BOOSTER rod and rubber boot passes through is available BEHIND some fibreglass on a MANUAL brake car there is a DIFFERENT GM part number for the pedal assembly in a POWER brake car. If you remove the fibreglass below the existing brake rod whole you are left with a keyhole that places the booster centered around it. The bottom holes are fine but need to be drilled out to accomodate the larger studs on the booster. The existing studs on the firewall need to be punched IN and the spring steel holding them in place needs to be either bent back or removed to allow the studs to come out from the inside. If you have a booster to firewall gasket then this makes a great template, else make one out of cardboard and use the booster as the template for it. You need a FOUR holes in a BOX pattern spaced 3&1/2 inches apart with the large booster rod hole in the middle. The result is that you need to drill two holes about 1/2 inch above the position where the manual booster hole was.

3rd the Brake switch push bracket
This bracket attaches to the brake pedal and is effectively what the brake switch pushes against. This is different for a power brake car. I don't have it yet (on order) but it will obviously move the position where the brake switch presses.

4th CLEVIS mount position on the brake pedal
The position the clevis mount to the booster rod has to be lower on the brake pedal in order to keep the rod perpendicular to the firewall. If you mount the rod to the existing clevis position it is at a slight angle. Fine when you have manual brakes but with a booster the ROD is connected to a diaphram and may cause wear. A previous CF post talked about swapping the CLEVIS position with the brake switch stop to align this properly.

Corvette Central sells a kit which pretty much has what I have including the brake pedal stop for power brakes. Ecklers measured there boosters and the rods were the same length on a CARDONE unit and a brand new unit they sell.

Thats where I am at right now. I am looking at two more rebuilt booster today and a couple of guys (thanks) are looking at the length of their original booster to see the length.

I am still not convinced that the rod length is correct but it may actually be a result of the different pedal assembly. The problem is that the ROD length does three things:
1. It keeps the brake switch ON as the pedal is physically an inch away from the switch
2. It does not allow the brake pedal spring to retun the brake to its extended position on the rubber bump stop
3. It robs an inch of brake travel which may be a safety issue.

Thanks for your input and when I resolve this I will get a tech article together......or maybe I just did. :smash:

If you see a flaw in any of my information please let me know. I want to get this installed right the first time.

:cheers:
Pete


[Modified by stingry, 10:08 AM 2/3/2004]


[Modified by stingry, 10:09 AM 2/3/2004]


[Modified by stingry, 10:10 AM 2/3/2004]


[Modified by stingry, 10:11 AM 2/3/2004]

stingry

Thanks.

:cheers: