power rod attacch is at a lower position and pedal is longer. Fred :)
My pointed little brain thinks, "That's strange. It has to mean that the power brake booster/master cylinder is mounted lower on the firewall than the standard master cylinder, or that the pivot is higher."
But that doesn't seem to make sense.
Are you sure that the difference that we're looking at isn't the 1979 model change.
I dunno! Just rhetorical questions as I sit here eating a ham sandwich w/potato salad.
Mike
Mike would like more info on this. The non power is out of an 80 and the power is out of 78. Fred :)
I did a manual to power brake conversion on my '76 wagon, and wrote a very thorough article on it in Pinto Times, showing the differences between the setups and how each part differs and/or how they interchange. I obviously cannot recount the whole article here.
Putting them side by side is an "illusion" which does not tell the whole story, because you are comparing the "ends" - the pivot point is different for each setup (meaning, the pedals attach in difefrent spots on the main bracket under the dash). The key here is the length of the rods, and where the rods attach. Both pedals in a vehicle would sit at the same height for the driver.
The manual setup needs a longer rod because the force applied to the master cylinder has to be greater. The power setup has a shorter rod because the power booster provides additional force that the driver does not need to. The master cylinder sits at the same height for both. AND, there is a different mount plate at the firewall for each setup.
Chris
Chris that all makes sense. I did measure master center line on both found that they were in the same place and another thing I noticed was the clutch pedal's were the same as meaning shorter then the brake pedal so the power brake pedal needed to mount higher to be even with clutch pedal. Fred :)
In the street rod world, the general rule of thumb is: manual pedals have ratios from 5:1 to 6.5:1 and power pedals 4:1 to 5:1, where you are comparing the distance between the pivot and where pressure is applied by the foot (i.e., the center of the rubber piece that your foot pushes on) to the distance between the pivot and where the master cylinder push rod attaches.
Carefully measuring with fingers (careful, now!) on the blowup of the pic on my monitor, it looks like the "manual" has a ratio close to 6:1, while the "power" has a ratio of 4:1.
So, the PLDP* thoughts are: the pedal pivot point is higher on the power brake car.
Thanks for the thought-provoking picture, Fred! 8)
Mike
*PDLP - Post-Lunch Digestive Period