Technical Front brakes not grabbing..... do I have gremlins?

The continuing saga of my 63 Olds Dynamic 88.
So far, I have:
-Replaced the booster/master cylinder with a universal booster and dual master cylinder (60s gm style for drum/drum car)
-Replaced or rebuilt all 4 wheel cylinders, cleaned all springs/hardware.
- Replaced every inch of hard line and all the brake hoses.

When I step on the brakes, my back wheels grab like crazy, but the front wheels don't seem to grab at all. I installed an adjustable proportioning valve on the rear today, and when I reduced the rear brakes, the front still didn't seem to grab much at all.

The only thing I haven't replaced is the actual shoes, which I'll be doing tomorrow.
Any other suggestions. I've never had this happen before.

TIA- Geoff

 

You should probably define "grabbing". I would get it up on jack stands and have someone step on the brake pedal while you try to turn each front wheel/tire.

 

Do you have a proportioning valve feeding both the front and rear brakes?

Are you getting a good flow of brake fluid when bleeding the front brakes? HRP

 

Actually, you want the rear wheels to lock up before the fronts, the sound of shredding rubber really impresses pedestrians and passengers. And yes, I'm off my meds again.

 

Why not replace the master and booster with original replacements? Not available? Universal parts, especially brake parts, universally don’t seem to work.


Did you adjust the brakes?

Sent from my iPhone using H.A.M.B.

 

Original Booster was trashed, (non rebuildable) and I wanted to upgrade to a dual master cylinder. Many years ago, I damn near totaled my 62 belair when I split a line. I have not had a single master cylinder in a car ever since. yes, the brakes have been adjusted.

 

Some master cylinders have different internal metering for front and rear. Have you tried swapping the ports?

 

Have you checked the Rod in the Master Cylinder if its not
traviling far enough into the Cly. your Brakes will not work rite!

And have you adjusted (bleed) the Car Right..??
Right Rear, Left Rear, Right Front , Left Front.??

Lust my 3.5 cents

Live Learn & Die a Fool

 

Maybe the rear shoes are contaminated? Brake fluid or grease? It’s possible they are locking up and grabbing before the fronts have a chance. Maybe focus on the rears, not the fronts.
Just throwing it out there.

 

Here is what I recently discovered, as I had chased my tail on the same problem for over a year. The GM brake shoes for a 57 Chevy rear end had asymmetrical brakes shoes and was designed for that. I will bet that other GM cars had similar arrangements.

As I recall, the forward shoe has 2 1/2" less material on it. All the auto parts stores are selling replacement shoes that have the same length of brake material. (The metal part of the shoe is same front or rear.)

After reading about this in the shop manual, I tried to purchase some correct shoes. The guys at the auto parts store said they can't get them. They then told me to take a die grinder with a cutoff wheel and cut through the brake material only. Use a chisel and pop off the short piece. It is glued to the metal.

After looking at the shop manual pictures, I cut 1" off the bottom of the shoe material and 1 1/2" off the top. Problem solved! I will bet you have the same problem. Look up some shop manual pictures of your brakes to confirm.

I got the crap scared out of me twice when the rear brakes locked up in a slight curve in the road. I was determined to solve that issue before I wound up in the ditch. Trust me on this one.

 

have new shoes arched, to make sure round - have shop mic drums to make sure that they are true - might need to be turned down very slightly