'75 Ranchero hydroboost upgrade

First to remove the actuation arm pivot pin.
This pin is welded in from the back side. Hence I ground off the weld and filed smooth thinking the pin would pop out. It would not. Took it to a metal shop where they heated the brake arm with the back side of the pin in a hydraulic press. "Pop" and out it came.

I believe I can clean up the pin and move to the new position - once I determine where that will be.

 

Yeah, that has to be a force-fit because of the strain that pin goes through.

 

For the next piddly problem, the hydroboost studs are not long enough for my '75 Ranchero - about an inch too short.



Is there a name for these bolts? I don't even see these on McMaster-Carr.

I could just use regular bolts BUT I have no help whatever and that makes it difficult to install simultaneously from under the hood and under the dash.

 

They're 'swedging' bolts. The fluted area is the 'swedge' to hold it in the hole.
But I have to ask: what is layered together that they end up too short? There really should only be the firewall and the pedal bracket; is the hydroboost body not making its way all the way in the hole?

 

Reuse the shouldered bolts that are in the plate I sent ya.Try installing linc. unit again.Make sure its flush against the firewall.Ranchero studs are extra long.

 

The original hydroboost studs are just not quite long enough. The vacuum booster studs were 2" long, longer than necessary. I have an alternative coming.

 

This should do - 2" long bolts with cap nuts to hold them in place. Even working alone I can position an Allen wrench under the hood while I tighten nuts under the dash.

 

That's interesting 5.0. I'll have to measure the length of my original studs. This hydroboost came from a 1977 Merc.

My studs measure 1-7/8" in total length or 1-3/8" exposed thread length. Are the Lincoln studs any longer?

 

5.0: You might check and see if your Lincoln hydroboost matches this one.

 

So the next problem is where to position the hydroboost actuation pivot pin relative to the brake arm pivot. I know from 5.0's experience with his '72 Ranchero that the original Ranchero location will bind with the hydroboost.

5.0's photo above shows a difference in the hydroboost actuation pivot pin relative to the brake arm pivot with Ranchero and Lincoln brake arms. Here I'm guessing the position of the brake arm pivot relative to the hydroboost mounting position may well not be the same for a Lincoln and a Ranchero; hence, a Lincoln brake arm alone might not work correctly in a Ranchero.

At 5.0's suggestion, I installed the hydroboost in my '75 GT and reinstalled the brake arm (a real pain working under the dash). I was then going to mark the center of the hydroboost actuation arm eye in its center position onto the brake arm with a Sharpie. Ha! I'm lucky to see anything under there and especially with a Sharpie in the way.

I was however able to mark the actuation arm eye extremes with a Sharpie on the brake arm using the Sharpie to push on the actuation arm eye. I assume I can use the median of those extremes as the best center position to install the pivot pin.

 

Probably overkill but made this 1/8" thick neoprene rubber gasket to go between the hydroboost and the firewall.



Any one need a template, send me a PM.

 

For my next challenge, I decided not to try and reuse the original actuation rod pivot pin that I had pressed out of the Ranchero brake arm. That pin measures roughly 0.552" (about 9/16" in) in diameter with an exposed length of about 0.838". I would have to drill a new hole in the brake arm for this pin and have it welded in place.

Instead, I found this heavy wall 9/16" tubing on McMaster-Carr with a 0.322" ID or just over 5/16" in. I had to buy a full foot of tubing but nothing seems to be cheap come Ranchero time.

My plan was to drill and tap a 5/16" hole at the proper location in the brake arm and attach an approximately 1" length of this heavy wall tubing for the hydroboost actuation arm pivot.

I think the actuation rod pivot to brake pedal arm pivot should be 3.65” center-to-center.

The first thing I found is that the pivot pin size is dictated by the size of the hole in the brake light switch - smaller than 9/16". Looking back, I wish I had just pitched that miserable brake light switch and installed a generic pressure activated brake light switch which I may have yet to do.

Easy fix for the tubing size. Not having a lathe, I mounted it in my drill press, spun it, and touched with a file which quickly brought it down to size.

 

These then are the parts to be assembled:

 

As assembled on the hydroboost activation arm. I plan to install the hydroboost unit as such and then thread the 5/16 bolt (I did use a grade 8 bolt for good measure) into the brake arm. Otherwise I'll never be able to assemble all this correctly from under the dash.

 

As they will attach to the brake arm when installed. I have added a spacer which I think is needed.