Hydraboost/Brake Pedal/Brake Light Switch Question

68/70Vette

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Torrance, Ca.USA
I installed a Hydraboost in my 70 to replace the stock GM power brake system. When I went to mate the Hydraboost clevis to the brake pedal, I had to move the brake pedal forward to match up the hole in the brake pedal and the hole in the clevis. With the holes matched up, I inserted the retainer pin. Problem: The brake pedal is now moved sufficiently far forward, that the brake light switch no longer "works;" i.e. the light switch plunger no longer touches the tab on the associated brake pedal bracket that opens the switch when the brake pedal is not depressed.

The brake pedal has two holes; the one on top is for the input shaft clevis for the manual brake master cylinder and the one on the bottom is for the input shaft clevis for the power brake master cylinder. (Top means the hole closest to the brake/clutch pedal shafts).

Is the Hydraboost meant to be installed in the hole for the manual brake system? If it is, the shaft going to the Hydraboost will be angled slightly i..e. the upper hole doesn't really line up properly with the Hydraboost.

If I wanted to use the second hole (the stock power brake hole), I'd have to have the aluminum spacer between the Hydraboost body and the firewall milled down. The spacer plate is about 3/4 of an inch and is located on the engine side of the firewall.

I tried calling Hydraboost and they no longer provide technical advice by phone. I called VBP, who I bought the booster from, and they didn't know,

Anyone with experience with this unit???Thanks
 
I have installed HB unit from a ebay unknown vehicle on to my '72 vette....in place of the vac booster...

long after I did my own rack conversion....not that is really has much affect on the HB install...I think....

Trick is, when doing the rack conversion years earlier, I had lowered the pedals for more comfort....auto tranny ...so just brake and gas was involved...

I just installed a HB on a antique chebby camper....so with my mighty TWO examples, I find that just bending the brake switch bracket or adjusting that long stem on the switch with the clamp nutz seems to pull it all into alignment....

I too have played with the vertical offsets on the HB actuation rod connection to the brake pedal lever...

I dunno what is ideal...except to say straight on seems better....but to locate that bastard right on with pedal height/driving comfort is a personal thing....

seems that on the truck/camper/van the angle is a bit off....still dive that SOB when required...

but the vette angles of the dangle is unknown as it stops on a dime with 9c change for some 5 years of daily driving..........:cool:

Semantics and such can get tough enough on a phone, let alone with typing...

:lol:
 
The hole in the clevis should be 5 3/4 inches from the mounting face of the Hydroboost (where it mounts to the firewall). You should attach it in the lower hole and attach the brake switch bracket in the upper hole. The bracket that the switch is in is adjustable and the switch body is also treaded for adjustment (unless you have a 1968). If you do have a 68, you will have to convert to a later setup.

44bfc7aa8dd039.jpg
 
The hole in the clevis should be 5 3/4 inches from the mounting face of the Hydroboost (where it mounts to the firewall). You should attach it in the lower hole and attach the brake switch bracket in the upper hole. The bracket that the switch is in is adjustable and the switch body is also treaded for adjustment (unless you have a 1968). If you do have a 68, you will have to convert to a later setup.

My brake pedal is now in a location where it doesn't touch the brake light switch shaft. I'll have to try to put some sort of a pad on the brake bracket tab that is supposed to depress teh brake light switch shaft.

I'd prefer to have it look corrrect. Either with a longer input shaft for the Hydratech or by milling down the aluminum spacer plate on the engine side of the firewall.

So far Hydratechbraking has not answered my emails! You can't call them either. Talk about technical support!
 
If your assembly is 5 3/4 you should not have any problems. Even with that, the switch bracket can be adjusted (see the slot in part #7 in the illustration above). Also you can move the switch in/out probably at least an inch.
 
Also you can move the switch in/out probably at least an inch.


Thanks but I'm already as far in as possible.....however...

I got a response from Hydratechbraking. (I retract my customer service comment in the above post). It was a timely response.


Since I only need a little extra length on the clevis, it was suggested I get a Dorman clevis that's 1/2 longer. It's Dorman part number 125-004.

The Hydratech response (Mr Paul Clark) stated that they didn't have fitment complaints like mind. He commented that the fiberglass thickness was variable from car to car since the glass was handbuilt. Actually, this may be the cause, or a partial cause. My 70 was in a front end collision, with damage FAR more extensive than I would have thought when I bought the car. The firewall was cracked in several places and was patched up.
 
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It depends which unit was ordered for your car. As I recall, Hydratech sells aa replacement for power brake cars, and one for factory manual brake cars. The power brake replacement the Hydroboost would be centered between the 4 mounting bolts. The manual brake unit is centered between the upper bolts, and is angled slightly downward, the top or the aluminum plate has a peak. I just installed one in my manual brake '69, my biggest frustration was re-installing the Clevis pin! Good Luck!!
 
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