70 GS parking brake not effective

I'm performing the annual smog and safety inspection of my country and the guys gave me a warning on the first attempt due to my parking brake isn't very effective, first attempt was 8% effective so proceed to change brake shoes, rear brake drums, adjust drums, adjust parking brake and now the effectiveness in the second attempt is 19% but still dangerous according to safety inspection technician. What can I do?

I agree is quite dangerous, in some hills I can feel the parking brake isn't enough to safely park the car

 

Please post the vehicle's year, make and model.

Are you using the correct emergency brake cable? It is correctly routed?

 

Is a 1970 Buick GS Stage 1, the parking brake cable is the factory one and I've never dealed with it so it should be correctly routed.

Maybe the issue can be in the drums? maybe I reassembled them incorrectly after the shoe replacement?

 

I'd disagree with Jason here, I think it's most likely cable related. Wrong cable or wrong hooks, or one or more hooks missing. Get it on a lift and take a pic, it's probably a visible thing. It's very common, I've seen it on almost every old car I've ever bought.

 

The pedal is hard to push, it goes like half way or maybe a bit more. The drums were machined but the new shoes were ordered in extra large size to fit the drums. According to the safety inspection the rear brake is working as expected so the only issue is with the parking brake so I think that discards brake shoes

Brake cable is stock and hooks are too but I agree that maybe something can be missing, I'm going to check today and post some pics

 

I may be way off here, but isn't some of the line inside a plastic tube or something? If it's factory original, the cable inside may be rusted to the point it won't allow the cable to move freely.

 

If it got worse after new shoes, then maybe the shoes need time to seat. Or the friction material on the new shoes is too hard.

 

My money is still on the cable(s)/hooks. If the pedal goes 1/2 way and stops, the brakes should be holding, oversize drums, hard shoes, whatever. It's a very simple system, but all the cables need to work freely, all the cables have to be right, all the right hooks have to be there, the geometry of the cable has to be right so that it pulls on both of the rearmost cables equally. Example? You could be missing the front rt hook that hooks to the cross member. Then you could have the wrong intermediate cable, too...like it could be shorter because somebody changed it because it was too long with that hook missing. The end result is that the whole cable geometry changes into a triangular shape and pulls one rearmost cable very hard, and the other...not so much. I think there are at least 2 different front cables, 3 different intermediate cables, 2 different length cross member hooks, and countless rear cables. Then there's the front cable that can go through, over or under the cross member. It will only work 100% right one way. Sometimes people put the wrong cross member in, or reverse it. People change transmissions...like TH350 to TH400, then the hooks and cables need to be right for the ap. Get a pic of the underside and I can maybe tell you if it's missing something. Look at this diagram...the intermediate cable geometry should look like this...fairly even geometry around it. there are small hooks 1/2 way down, if one or both are missing, then it doesn't pull the rearmost cable straight, it won't go as tight as it should.
https://www.opgi.com/cutlass/C990244/

 

I would be inclined to remove the drums and observe the action of the handbrake cables and with a helper in the car, test to make sure there is no resistance in the cables, in other words, moving freely when applied and released. Remember to not push the foot brake pedal with the drums off so you don't pop the wheel cyls.
If the cables test completely free and the shoes are new, examine the shoes to see if they are contacting the drum just in the middle or at the ends of the shoes. If this is the case, I would find a shop that has the ability to arc (grind, match) the shoes to the drums to ensure complete contact. You will have to bring the shoes along with the drums to the shop. Once this is done, you will have much more surface contact shoes to drum. Eventually, as the shoes wear in this will start to happen on it's own, but grinding the shoes to the same radius as the drums, will likely clear this issue up right away. Good Luck!