Putting booster on 66 drum brakes driving me crazy

[buildinga55]

Thanks, I will take a look. However, this has new hoses, new lines for half of the front anyway as I split the line when I put on the dual MC, the MC is new, the wheel cylinders are new. The only thing on the front brakes that has not been replaced is the one line where it was split that goes to the passenger side. However the brakes bleed fine and the fluid is clear so I have to think that like is ok. I will take a look at the site. I would like to find the cause since it looks like I now have the truck for the rest of the weekend.

Thanks

[old cool]

hey 55. did you ever get the brakes right? Since i keep an eye open for new ideas, I like to share when I find something. I googl: Brake Trouble Shooting Guide - Classic Performance Products. Seemed like someone there did a lot of work to help with brake probs. No joke. Very easy read. (I have no connection to them.)
I know you understand the diff between deep bore MC for manual brakes; and shallow for power brakes; however, I did not and therefore will order my MC accordingly.

[buildinga55]

The truck is still not stopping like we would like but much better. All the listed items are new mc,wheel cylinders,brake pads lines hoses additional vacuum tank. . Maybe this is as good as the old truck is going to stop.

[LostMy65]

Originally Posted by 66pnl

I have a couple. One is 1.425. The other is more of a bullet shape so it kinda matches the bottom of the hole. It is 1.522 overall. I recently found that the holes in the aftermarket masters are larger diameter than the oem remans that I've used. The aftermarket (cpp) are slightly over 1/2 in. (The bullet is .535). IIRC I used a 3/8 or 7/16 bolt and sanded the threads down to fit the smaller bore.

I know this is an old thread, but I just figured out how to get the correct length for intermediate rod (bullet). Measure the depth of hole of the drum/drum master cylinder from mounting surface. Then measure the depth of the hole of the disc/drum master cylinder to mounting surface.
Cut the bolt to the length of the drum/drum minus the depth of the disc/drum.

[old cool]

Thanks for message. i no longer have gmc but i did adjust a booster rod on a 72 vette measuring as you did. it worked but my pedal seems a tad lower. aftermarket parts are sometimes the problem. i tried to lengthen the rod but the master cylinder depth will not allow. the rod hits the cylinder face and you cant bolt MC to booster. Brake work seems more problematic then decades ago.

[LostMy65]

I wanted to give an update for how mine was going.
I made an intermediate rod (bullet) using the method above for determining the length. I made it maybe 1/16 to 1/8 longer because I figured it's better too long than too short. The brakes are dragging ever so slightly, so I'm going to grind it down a little shorter and try it again. Otherwise, the booster makes a huge difference in how much peddle effort is required to stop the truck.

[old cool]

I have read on Vette forum that some back off the nuts on MC ( this widens the gap between the rod and the center of the closed MC piston.)
this may tell you if the rod is too long if drag goes away. If the rod is too long, Im surprised you were able to bolt the MC to the booster.
I adjusted my rod thinking it would raise my pedal. The pressure and springs in the MC will not allow.
I share for conversation only. Im not a mechanic. Good luck.

[LostMy65]

Originally Posted by old cool

I have read on Vette forum that some back off the nuts on MC ( this widens the gap between the rod and the center of the closed MC piston.)
this may tell you if the rod is too long if drag goes away. If the rod is too long, Im surprised you were able to bolt the MC to the booster.
I adjusted my rod thinking it would raise my pedal. The pressure and springs in the MC will not allow.
I share for conversation only. Im not a mechanic. Good luck.

Great idea. I'll give that a try and post back.

[LostMy65]

That did it.
One washer and it rolls freely now.
Thanks again.

[LostMy65]

I just wanted to give another update.
The brakes work great. The bullet works. And adding washers to fine tune was a great suggestion.