You can use a 7/16" or 1/2" drill to just remove the threaded portion of the swedged inserts, or you can completely remove the threaded inserts.  When I do them, I remove the threaded inserts and weld a thick washer over the hole (using the booster studs as a template to be sure the washers are in the right place).  Or, once you removed the swedged inserts, you can just place a washer under the nut after installing the booster. FOUR HOLES will have booster studs going through them, including the new hole at the botto, center.

REMEMBER, the upper driver side swedged insert does not get drilled or removed. It will receive a short bolt from the engine side of the firewall.

On the plate, the bolt hole with the arrow holds the plate to the booster with the one short stud on the booster.  That stud does not touch or go through the firewall.  If it is longer than necessary, it can be cut off.

Without all the parts, things get sloppy and stoplight switch may not function properly

MS wrote:

Without all the parts, things get sloppy and stoplight switch may not function properly

That image only shows a single nylon washer, where does the second nylon washer go?

Alan wrote:

i found some plastic washers in the hardware section at local Walmart. They would have to be drilled out as they were like for a 1/4" bolt.. Picked them up figuring they might come in handy somewhere. They were about 1" OD.

 
Those parts are pretty specific, not much cash, and readily available. Get the correct parts.

I have seen Mustangs come into my shop that had no bushings whatsoever on the brake pedal and, miraculously, the stoplights still worked. Not something I would try.  The correct parts assure no rattling and proper stoplight switch operation.
That said, some 67-69 cars have stoplight issues even from the factory.  I finally gave up and went with a pressure switch on mu factory power brake 69..  I know exactly how to put them together and never got them to work until I put the pressure switch on.

Its magic, I tell you, how those stoplight switches operate!

MS wrote:

I have seen Mustangs come into my shop that had no bushings whatsoever on the brake pedal and, miraculously, the stoplights still worked. Not something I would try. The correct parts assure no rattling and proper stoplight switch operation.
That said, some 67-69 cars have stoplight issues even from the factory. I finally gave up and went with a pressure switch on mu factory power brake 69.. I know exactly how to put them together and never got them to work until I put the pressure switch on.

Its magic, I tell you, how those stoplight switches operate!

I remember when I was going through changing from manual to power brakes and I had installed a power brake pedal from a 69 - and I didn't know about the differences in power vs manual switches - I almost got rear ended because the manual switch required more pedal travel. I was starting to stop way before my brake lights were coming on. I looked at the switch, and for the life of me, I couldn't figure out how that switch worked. I found out that there was a different switch for power brakes and I swapped the switches out. MS - you're right - is has to be PFM that actuates that switch! (PFM - pure f**king magic)

 

One step above touching two bare wires together when you hit the brakes.
Some bare wires and careful application of duct tape to the pedal support and pedal could probably make it work, but that’s not how I would do it.
I tried two or three different power brake stoplight switches on the 69 before I got tired of crawling under the dash and plumbed a pressure switch into the front brake line right beside the master cylinder

For my 65, I had two stop light switches and didn’t realize the switch for manual and power brakes were different.  I believe what I installed was the ‘manual’ switch, which was an original from a 66 Mustang, and it worked fine with my original manual 4-wheel disc brake setup.  I did not change the switch when I installed the hydroboost system a couple of years ago, and is still works just fine. 
I checked it again today, in the garage, with the engine off, when I press the brake pedal the stop lights come on prior to me providing any real pressure on the pedal. 
Just saying.

Good point, I'll check it out and respond back. 

MS wrote:

I have seen Mustangs come into my shop that had no bushings whatsoever on the brake pedal and, miraculously, the stoplights still worked. Not something I would try. The correct parts assure no rattling and proper stoplight switch operation.
That said, some 67-69 cars have stoplight issues even from the factory. I finally gave up and went with a pressure switch on mu factory power brake 69.. I know exactly how to put them together and never got them to work until I put the pressure switch on.

Its magic, I tell you, how those stoplight switches operate!

@MS, got the booster installed but had a question. The instructions say to install the included lock washers and locking nuts on each bolt...but my booster just came with nuts that had the serrated flange...no locking washers. Do I need to get locking washers to go with the serrated flange nuts or are they enough?
 

Before you finish assembly of the booster, put an extra nut on the studs where they pass through the mounting plate of the booster with a bit of loctite. Place a fender washer on top of the extra nuts and set the top of the washers to the same height as the edge of the mounting plate. This will give a solid surface to tighten against.
 

Last edited by 50vert (1/11/2024 10:12 PM)

Phydeauxman wrote:

50vert wrote:

Before you finish assembly of the booster, put an extra nut on the studs where they pass through the mounting plate of the booster with a bit of loctite. Place a fender washer on top of the extra nuts and set the top of the washers to the same height as the edge of the mounting plate. This will give a solid surface to tighten against.
 

Great tip...thanks

Yes, this works well. I have used a stack of washers. That way you are sure to be tightening the booster itself, not just a nut on a threaded stud