Firewall Bracing For MC?

[Jesse Z]

I see many of you use firewall mounted master cylinders. And suggestions regarding how should I brace the firewall and mount the MC to prevent flexing during brake application?

[bowt1ed]

A few of us have used CPP's booster/master mount kit, which triangulates the firewall and dash. Very strong. Prior to that, I had a 2nd Gen Camaro booster/master and it was supported adequately. If I were staying with it still, would probably fab another support bracket to dash though.

Cheers, Jim

[Oldtruckwelder]

The cpp system is really nice and braced
JT from SC

[mr48chev]

I used a piece of plate about a foot square on the inside of the firewall on mine when I had the firewall mounted mc. Had the pedal bracket tied into the dash too. Never had a flex problem. I had a mastercylinder/booster and pedal assembly out of some rig I scrapped out but can't remember what. I just remember the booster was big and ugly but worked great.

[Jesse Z]

Originally Posted by Oldtruckwelder

The cpp system is really nice and braced
JT from SC

That looks like a problem solver that will get my truck on the road quicker. Thanks!

[Oldtruckwelder]

Originally Posted by Jesse Z

That looks like a problem solver that will get my truck on the road quicker. Thanks!

The CPP system is top notch and has some options at order.
Some of the cons are the existing brace/bracket needs to be cut out under dash. And really minor you will need to add your brake light switch of your choice.
JT from SC

[whitedog76]

I’ve pulled brake pedal assemblies from 03 and newer GM vans and pedal assemblies from Jeep TJ’s. The Jeep was spread out a little more probably not needing firewall reinforcing, but the bracket itself seems a little weak. The GM van pedal is about as beefy as it gets, bolt it up and go.

[Jesse Z]

Originally Posted by whitedog76

I’ve pulled brake pedal assemblies from 03 and newer GM vans and pedal assemblies from Jeep TJ’s. The Jeep was spread out a little more probably not needing firewall reinforcing, but the bracket itself seems a little weak. The GM van pedal is about as beefy as it gets, bolt it up and go.

Thanks, now I know where to start looking!

[roger55]

I used the one from CPP.
I'd without a doubt buy it again but I did do some modifications to it to make it a lot better.
There are issues that need addressing if you want to be really happy with it.

All the details are in my build thread.
See posts #242, #279 and #416.

Looks like oldtruckwelder and I both decided to weld the plate to the firewall to make it stronger and look better too. I welded spacers under the plate for more support first. I'd guess he did the same thing.

It also looks like he mounted a brake light switch very similar to how I did mine.



Btw, here's the entire kit as received:



I also found a major flaw in the instructions that would have lead to a dangerous situation If I hadn't noticed it:

The instructions state to drill out the 3 rivet holes (used by the OEM to hold them to the drum) to 3/8". This is too small. Their machining isn't accurate enough and a little extra space is needed around the bolts. I went to 13/32" for them. Plus, those same holes need to be chamfered so the 3 bolts (with the tapered heads) they supply will seat properly and pull their plate tight to the hub. I chamfered the holes with a 1/2" drill bit.
I first did it their way and the plate would not pull tight with the hub. If left that way, the assembly would not be in single shear and could lead to failure of the lugs and wheel loss.
Check this with your kit if you buy it. I talked to another person who bought the same kit, and they didn't have this issue.

Here's the hub after I chamfered the the holes. Also look closely in the upper right of the photo where you can see shoulders of bolts protruding through the holes in the plates. Without the chamfer, these would hit the hub and not allow the plate to cinch up to the hub all way. This would be super dangerous and cause failure to the lugs and a possible wheel loss while driving.



As I said before, I also drilled the holes with a 13/32" bit. There was some binding with them being 3/8" but seemed fine with the slightly bigger hole.