Hot Rods Help me troubleshoot poor brakes

Done - I was able to get rid of sone free travel, but didn't help with stopping power

 

Yes. and Yes.

 

Have you confirmed that the caliper pistons are actually moving?

 

This is just a guess, could their be a vacuum problem or not enough?

 

I've already had to adjust the rod where it has zero free play to get more pedal. Jack up one of the front tires off the ground, keep adjusting on the rod until the tire starts to drag a bit. Back it off a turn and go for a ride. Bring tools along in case the car stops itself due to pressure build up from heat and driving. If it does start to drag the brakes, back it off another1/2-1 turn. Aftermarket cheap brakes aren't machined all too well. Good Luck.

 

I've looked into this as well. The engine has a basic stock cam. Someone before me out a vacuum canister in trying to solve the same problem, event though not needed.

 

WHAT? First of all, the rod in the MC has to be adjusted just loose enuff (ie the piston is all the way to the rear of the MC) that the fluid that was pumped out into the brake lines (when you stepped on the brake), can return to the master cylinder when you release the brake pedal. After that, there is NO adjustment made to the MC brake rod at all, other than an additional bit of slack to create 1/2" or so of pedal play before brake application.

 

Trust me that is conventional thinking. I've had two different systems in the last 25 years that the piston in the MC had to be compressed a 1/16" or so for the brakes to function properly with good pedal. The brakes never dragged and 30-40 thousand miles were put on each vehicle as stated. Back when things were rebuild and machined properly, this was never an issue. Take it for what it's worth, not telling just stories...

 

I looked up the caliper specs you said you are using:
for a ‘72 Monte Carlo the calipers have a 3” piston,
That car with front disk brakes has a 1-1/8” master cylinder bore.

so if that is what you are using then it shouldn’t be the calipers or master, they are matched. It’s either pedal ratio, blocked lines or bad parts.

 

Are the caliper brackets constructed to properly locate the calipers and permit free movement during during application

 

My thoughts were the same, but was reminded that using a smaller booster than original was different than the OE setup. I've got a 5:1 pedal ratio, and have verified that the calipers are moving and thre is plenty of fluid moving through the system.

 

What is stopping you from using a larger booster? is it diameter or length?
My wagon has a ‘93 mustang cobra booster. It’s deep but a smaller diameter than most large boosters

 

Both. Diameter prevented by frame rail, depth prevented by frame x member that has already been notched to fit master.

 

It might help to get a set of these brake pressure gauges to help diagnose your brake issue with actual data. Otherwise, it seems like a lot of guessing. They're not expensive and it might save some time.

https://www.summitracing.com/parts/sum-800114

 

Here's an off the wall suggestion.

Swap the lines on the master cylinder, could be possible the rear brakes are applying first, expanding out to the drums stopping the pushrod from engaging the front brakes fully.

When I first built my t-bucket I had under floor master, proper rpv's and adjustable proportioning valve. I could never get the front brakes to bleed, just foam out the bleeders, made a thread here with lots of suggestions that didn't work. I had a few different guys come over, some of them professional car builders and nobody could figure it out.
On the umpteenth day of screwing with it I removed the proportioning valve and the damn thing bled like normal ! The valve was throwing the fluid to the back brakes, expanding them out to the drum stopping the pushrod from compressing the front chamber of the master all the way.
I later re-installed the valve with it adjusted to let the front brakes get the majority of the fluid first and never had an issue again.

 

I just bought new shoes for my 51 Victoria and the new shoes have linings that are thinner than the old worn leading shoe.
The HAMB needs a separate forum just for brakes

 

I dont recall seeing you utter these prophetic, wise words for a while! Always makes me smile!

Chris

 

No doubt about it, sure can learn about what is going on from a brake pressure gauge.