Master cylinder/firewall flexing?

[icetech]

Hello, on my '62 recently i was doing something and noticed when i hit the brake pedal the whole MC will flex upwards a bit (like 1/2" if i really press hard) This weekend i was at a guys house who has a 62 he races and he full forced the thing and the MC didn't budge a bit.. Am i missing something here? My firewall had no rust and isn't thin or cracked.. the car was a family truckster til parked so no really abused... or is some flex normal?

This is my setup (i believe the MC is mid 70s a-body that bolted into the stock holes.)

 

[glorydays]

my 65 moves some as well.

 

[icetech]

my 65 moves some as well.

ok cool... i know the engineering wasn't top notch back then but seems that flexing so much would lead to cracks.. i way overthink stuff though..

 

[gkent]

Doesn't help your situation BUT ... there is more force on the firewall with manual brakes.

 

[icetech]

Doesn't help your situation BUT ... there is more force on the firewall with manual brakes.

true.. i was just double checking... the one i saw was using the 2 bolt alum/plastic MC and didn't budge at all...

 

[gkent]

Being a race car he may have had a reinforcement behind the firewall.