47-55.1 excessive travel in brake pedal.

[nvrdone]

ok folks, as some of you may remember Ive been fighting a brake pedal with too much travel. The pedal goes down within about 3" of the floor before the brakes engage. Its a power brake conversion. Anyway many of you have offered suggestions which I appreciate.
so last weekend I was doing some research and found an article that talked about adjusting the push rod / m.c . piston clearance. WHAT THE HECK ???
I'd never heard of such a thing. So i pulled the booster & m/c out of the truck and measured the clearance. It's about 1/8". This article says the clearance should be about .020. The article also showed a special tool for adjusting the clearance. So now I need to find that tool. Or maybe I can find a way to measure it and get close.
Wish me luck.

[28TudorAZ]

I had a similar issue with a power brake conversion. It ended up being a combination of the push rod adjustment and a bad master cylinder.

[jweb]

You need one of these tools to set the push rod depth. I have one, if you need to borrow it send me a PM with your address and I'll put it in the mail. Send it back when you're done.

https://www.ebay.com/itm/power-brake...-/232919566152

You may also want check your pedal ratio:
https://techtalk.mpbrakes.com/how-to...ng-pedal-ratio

[mr48chev]

I've fought the Bendix vs Delco master cylinder to booster thing before. That is usually a huge difference though as one has a lot deeper recess in the piston for the push rod. One way the push rod bottoms out in the master cylinder before you get the cylinder bolted up, the other way you run out of travel before it moves the piston far enough to work the brakes but normally you catch that when you take the MC out of the box. Or you learn to.

This is the first time I ever have seen that tool, a search shows that it is a copy of a tool that is used in dealerships. The mechanics probably never knew about them unless the factory service rep said they needed one to solve a similar problem.

[nvrdone]

guys thanks for the help. Jweb - i just ordered that tool on amazon. should be here by this weekend. Also found the booster has a bad seal on the pushrod side, so its going back to the supplier tomorrow.
my pedal ratio is at 4:1 so thats one of the reasons i couldnt figure out why there was so much pedal travel.

[geezer#99]

Could be the m/c bore size is a factor!
How big is the bore on yours?

[nvrdone]

m/c bore is 1" - same as stock m/c.

[geezer#99]

Have you considered trying a smaller one.
Like 15/16 or 7/8.

[nvrdone]

the m/c & booster are all part of a kit from Performance on Line.

[geezer#99]

Seems that using a complete kit these days usually means you need to replace a couple parts with ones that work for your application.
Brake kits seem to be the worst.
7/8 inch bore m/c came on 78 monzas. About 60 bucks. They look stock. Wilwood have fancy looking ones.

[dsraven]

you can whip up one of those tools out of plywood or scrap metal if in a pinch.

[nvrdone]

i sent the supplier pictures of the blown out seal and they agreed its a warranty issue. so tomorrow I ship the damaged one back to them. When they get it, they will ship me a replacement booster. so we will see how this goes.
Thanks for the comments.

[hogfarm]

My friends truck had the same problem ,to much travel on pedal,Have a lathe so I just made a sample rod,it was still short but we then knew how long to make the new rod.worked great

[nvrdone]

woo hoo - i have brakes !! Sent the defective booster back to performance on line and of course UPS lost the darn package. So POL sent me another booster and I got it today. But guess what - the one I sent UPS came back to me today. Anyway, I installed the new booster tonight and the pedal now goes down about 3" and stops. Havent driven the truck yet, but thats major progress.