Power brake booster bracket - bolt specs?

[Banjer Picker]

I’m missing a few of the OEM bolts that fasten the brake booster bracket to the firewall.

Trying to find identical ones to replace the missing ones but can’t seem to identify or locate ones with similar specs.

The Ford OEM bolts seem to have a bit of a taper, no threads for the first 1/8th of an inch and a “captured” washer.

Went to ace just to see if I could find a couple standard bolts and washers to use instead and they do not work (tried the fine and course just in case)

Couldn’t find much on the web or the CB site either.

Kind of stumped on what seems like it would be a pretty straight forward item.

 

[904Bronco]

I have always replaced the bolts/washers with Grade 8.

Got a picture of what you are specifically looking for, I might have some in my take off bucket...

 

[Banjer Picker]

Yeah, I actually have 2 of the OEM bolts here in my hand so I have a physical reference. I took those up to the Ace hardware with me and got grade 8 bolts with the same thread pitch and length but they do NOT like getting threaded in at all. When I compared the new bolts to the OEM bolts I have, the OEMs seem to taper down from the head to the en of the bolt which is what I am assuming is preventing the new bolts from threading into the old holes. May take ya up on your offer if i can’t solve the “mystery” in this thread. LOL!

 

[904Bronco]

Copy...

 

[SLOWnEASY]

Out of curiosity what was the correct bolt that matched? Was it something like 5/16 fine thread? Do you have a set of taps and dies? When I run into things like what you are describing I usually run a tap and die over the new bolts and also the bolt holes. Usually I can't even see any metal getting shaved off the threads but magically they screw in fine after.

 

[catfan]

3/8 course .

 

[Oldtimer]

Appears the bolts that hold brake booster bracket also hold the pedal bracket assembly on other side of fire wall.

The Ford MPC does not acknowledge power brakes in 76/77 Bronco?

I think the bolts you are looking for are 57477-S.(nobody sells them)
3/8-16 X 3/4" thread, hex head, conical 1" washer, with lead point, GR5.1

If a 3/8-16 bolt won't screw into firewall, you may need to loosen all bolts holding pedal assembly and move it a little.

I can't find a description for 38542-S bolt, but would guess it has similar threads, and is longer, to also pass thru flange on master cylinder of a NON power brake Bronco.

 

[ntsqd]

Close enough?

https://www.auveco.com/hex-hd-sems-body-bolt-w-dog-point-3-8-16-x-1-3-16-black-23664

 

[904Bronco]

Is this what you have? This is from my 68...

 

[Banjer Picker]

Out of curiosity what was the correct bolt that matched? Was it something like 5/16 fine thread? Do you have a set of taps and dies? When I run into things like what you are describing I usually run a tap and die over the new bolts and also the bolt holes. Usually I can't even see any metal getting shaved off the threads but magically they screw

Out of curiosity what was the correct bolt that matched? Was it something like 5/16 fine thread? Do you have a set of taps and dies? When I run into things like what you are describing I usually run a tap and die over the new bolts and also the bolt holes. Usually I can't even see any metal getting shaved off the threads but magically they screw in fine after.

It’s a 3/8” corse thread of some sort for sure. Just weird that I can pull the OEM bolt out of one hole and it threads right it to any of the other bracket holes but if you try to screw a standard (non OEM) 3/8” course thread in, it doesn’t want to go in at all!

 

[Banjer Picker]

Appears the bolts that hold brake booster bracket also hold the pedal bracket assembly on other side of fire wall.

The Ford MPC does not acknowledge power brakes in 76/77 Bronco?

I think the bolts you are looking for are 57477-S.(nobody sells them)
3/8-16 X 3/4" thread, hex head, conical 1" washer, with lead point, GR5.1

If a 3/8-16 bolt won't screw into firewall, you may need to loosen all bolts holding pedal assembly and move it a little.

I can't find a description for 38542-S bolt, but would guess it has similar threads, and is longer, to also pass thru flange on master cylinder of a NON power brake Bronco.

View attachment 951515

View attachment 951516

View attachment 951519

Now that’s interesting! So by “conical”‘I’m assuming that does mean that it’s “tapered” as I suspected? Thanks for the in depth input and pics!

 

[Banjer Picker]

Is this what you have? This is from my 68...

Not exactly. Tye bolt heads on mine are not flanged and they have a washer that is captured but spins freely (just doesn’t slide down the threads) I’m not married to using the OEM stuff, just don’t want to try to cram a bolt through that’s going to cause trouble later if I have to unscrew it.

 

[Oldtimer]

Now that’s interesting! So by “conical”‘I’m assuming that does mean that it’s “tapered” as I suspected? Thanks for the in depth input and pics!

Conical applies to the washer, it has a slight dome to it.
The bolts I listed were to hold pedal support to firewall, and the larger washers were to spread the load on sheetmetal firewall.
You have the the booster bracket to spread the load, so bolts with star washers, like 904Bronco showed, will work.
Does a 3/8-16 nut screw onto the original bolts?

 

[ntsqd]

Here ya go: https://www.auveco.com/products/bodyhardware/boltsbodyhardware/bodybolts Should be able to find what you want there. The SKU's that I've tested all have shown on amazon.

 

[904Bronco]

So you don't have the early style, so it must be these...

 

[Banjer Picker]

So you don't have the early style, so it must be these...

Yessir. That’s exactly wha I have.

 

[Banjer Picker]

Conical applies to the washer, it has a slight dome to it.
The bolts I listed were to hold pedal support to firewall, and the larger washers were to spread the load on sheetmetal firewall.
You have the the booster bracket to spread the load, so bolts with star washers, like 904Bronco showed, will work.
Does a 3/8-16 nut screw onto the original bolts?

The OEM 3/8” bolts go in with no issues. The non-OEM, 3/8” course thread bolts that I got at Ace do not want to go in at all.

 

[samamarshall]

Ran into this same problem...didn't want to use the old rusty OEM. I had to run a tap into all the threads to clean them out, possibly had some sealant or something in there from the firewall? Anyways some standard 3/8" grade 8's went right in after that. Had one I couldn't run the tap in, so just sent it and it came back out fine.

 

[904Bronco]

Thread cleaner or tap if that is all you have... Is a great suggestion.

 

[ntsqd]

I've seen this before with older Fords. In those cases it was that the OEM tap had a slightly smaller crest diameter due to it cutting a larger radius in the root of the female thread. Makes for a stronger thread, but means that not just any bolt will screw into them.