65 Firewall brake pass-through

[kevinshi]

Hey folks...

I have couple of questions about the brake pass-through on the firewall on my 65 Caliente... for the moment I will keep it simple...

Which (if any) of the 10 holes noted in the below picture is NOT stock?

[poboyjo65]

this is my 65 manual brakes car. PB cars the holes & bolt pattern were different. looks like what may have happened to yours. comethead had to change his I think. but this pic may help;

[kevinshi]

Super, many thanks.

I now think my car did indeed have original power brakes (later replaced by an upgraded booster, dual reservoir master cylinder and proportioning valve).

Does anyone know whether perhaps the original power brakes were a post-factory installation (aka dealer install)? That would explain why I have two holes. E.g. the upper hole (9) is the original factory hole where as the lower hole (8) was subsequently hacked into the car for the power booster.

FWIW: I believe power brakes hole had to be lower because the original booster was 9" in diameter and would not otherwise fit under the driver's side engine compartment diagonal support brace. The booster compensated for this "lower" position by having a receiver hole (at the end of its brake pedal shaft) that was off-center and elevated as per the below picture of an original booster. As such the optional power brakes could be added w/out having to replace the brake pedal.

[poboyjo65]

Yes pb cars the holes were in different locations. Comethead will come along & can tell you which is which.

[comethead]

Yup I had the same thing going on. The lower hole was hacked open for the stock power booster. I think you’re right that it was dealer installed because the added hole was pretty ragged.
I patched the lower hole and installed a manual dual MC.

Joe

[kevinshi]

I patched the lower hole and installed a manual dual MC.

Joe I am fabricating a patch right now... any advice?

[poboyjo65]

one thing I remember is the under dash brace that attaches to those same 4 holes on the inside has the 4 caged nuts on it,be careful with it those little tabs that hold the square nuts on will break easy . also it is hard to get reassembled by your self. but it has one sheet metal screw to hold the brace up there until you get a couple of the bolts in from the engine bay side,(the 2 in the pic above the big hole). you screw the one sheet metal screw on from the cabin side though. here is a close up of the manual brakes holes, the sheet metal screw goes in the small hole to the side between the big mounting bolt holes.I cant remember which one.

[kevinshi]

...the under dash brace that attaches to those same 4 holes on the inside has the 4 caged nuts... it has one sheet metal screw to hold the brace up there until you get a couple of the bolts in from the engine bay side... you screw the one sheet metal screw on from the cabin side though

Super helpful, many thanks.

I was thinking that those square holes on the pedal brace looked like they could host cage nuts - great to have that confirmed! However:

• the lower holes must not be cage nuts, eh? I say this because the studs from the master cylinder (or booster) pass through the lower holes... and you can't use a cage nut to secure (two) posts...
• the upper holes were not (I think) used when the power booster was installed - because the booster itself effectively blocks access to them. They may still have had cage nuts installed but those nuts would have, I believe, been left bolt-less. Either that or the installer had extremely small hands and somehow got a bolt squeezed in there from the engine side...

"One sheet metal screw" - thanks for explaining that!! I was wondering what the heck that little hole was for... (... and in fact I think you have now solved another mystery for me - there are a similar holes on both of the convertible housing extensions... which also makes sense as a "temporary" sheet metal screw to hold it in place until the convertible top frame was later installed).

Just for posterity (using the below picture for reference):

• the upper red circle marks a recess in your fire wall. I believe that is a center point for the hole saw that was used to cut in the lower brake hole (the hole where the original power booster passed). I don't have this recess in my firewall because, of course, it was cut out when said hole was cut for the original power booster.
• the lower red circle marks another recess in your fire wall. In my firewall there is a ~5/16" diameter hole. I believe this hole is where the 3rd (lower) stud on the original booster passed.

[poboyjo65]

I would guess on PB cars the cage nuts are removed but on manual brake cars all 4 holes are cage nuts. I remember having to get longer bolts because the adj proportioning valve bracket mounts on those 2 holes to the sides of the big hole,the old ones just wouldn't get started with the extra thickness of that bracket. but I think the power booster studs ,the top 2 go in holes 10 & 6 ,then the bottom stud goes in number 7 on your pic. so if you are going to manual & you are filling the un needed holes I believe 7 & 8 are the main ones to fill. you might want make a reinforcement like the top 2 holes of my pic, for the pedal brace since they did it at the factory for man brks.

[kevinshi]

I would guess on PB cars the cage nuts are removed but on manual brake cars all 4 holes are cage nuts.

Ah, of course. The manual master cylinder had holes on it where a bolt passed through... and then through the firewall... and finally screwed into the cage nut on the lower holes of the pedal support brace. Got it.

Meanwhile when power brakes were installed (as you say) those two bolts on the master cylinder became studs on the power booster... and as such the lower cage nuts had to be removed and replaced by nuts (and probably some kind of washer as well).

[poboyjo65]

Right. spot on. & one other note; your pushrod will mount to the brake pedal arm higher than PB did.& may be some of the reason they had 2 different locations. needs to be higher on manual brake pedal arm for more leverage/less effort or/and lower for power brake pedal arms for less leverage which would be touchy brakes ,,,too sensitive. those 2 reasons & what you mentioned ;more room for the booster.

[poboyjo65]

[

Just for posterity (using the below picture for reference):

• the upper red circle marks a recess in your fire wall. I believe that is a center point for the hole saw that was used to cut in the lower brake hole (the hole where the original power booster passed). I don't have this recess in my firewall because, of course, it was cut out when said hole was cut for the original power booster.
• the lower red circle marks another recess in your fire wall. In my firewall there is a ~5/16" diameter hole. I believe this hole is where the 3rd (lower) stud on the original booster passed.

That's a pretty good theory, I bet you're right.

[kevinshi]

For what it is worth, here is what I came up with as a delete plate for the lower (original booster) hole.

This picture is taken from the driver's perspective as though you are looking through the firewall with x-ray vision.

The top two bolts are booster studs that pass through the lower holes on the brake support. The lower bolt fills the hole used for the 3rd bolt on the original booster (unnecessary but I put it there anyway). The curved on the bottom/left is shaped to wrap around the firewall's oval-ish steering column hole. I used 16 gauge sheet metal primed/painted and finally covered with undercoat.

If it looks like a hack its' because it is one. .

[lavron]

If it looks like a hack its' because it is one.

That is pretty good hackery and that is coming from someone that knows a thing or two about hackery someday I might even be as good as Fred but in the meantime, I compliment you on a neat looking piece that will never be seen or noticed.

See Ya,
Mike

[kevinshi]

...a neat looking piece that will never be seen or noticed.

My 16 year old son, while helping me adjust the rear bumper by 1/16th of an inch: "Does it really matter?"

Me in response: "Nothing on this car really matters."