I have a 76 Camaro 305 auto it’s been leaking through that port there’s a slit in the center of it causing it to leak through I was wondering if I can weld each hole shut (without covering the slit) since it has no threads. it looks like A breathing port but I’m not sure. I do have breaks but I have to slam on them. there’s no air in the system. So my question is, is it possible to weld both sides without any issues or what kind of issues will it cause

 

No its not safe, even if you understood what the vents do the heat from the welding process could damage the seals inside. In most cases when fluid is being pushed out of the vent that is just a symptom of the real problem. Fluid is getting past the internal seal. The reason for the vent is so you do not build pressure on the "other side" of the seal. If you built pressure in the vented area it could stop the piston from moving forward at all.(no brakes at all, front or back)

You can either rebuild the master cylinder or replace it. Generally it is not worth rebuilding one because you can buy a rebuilt one for $10-15 dollars more then a rebuild kit. Makes sure you you watch a youtube video on the proper bench bleeding process and on car bleeding process.

 

As usual Gorn is spot on,a new Master is the only fix but they really aren't very expensive if you shop around.
You can rebuild it with a kit if you know what you're doing but for my money the difference in price isn't worth the hassle.
About $40,some are less but I'd buy from a quality source like NAPA if it were mine.
That's a part they should have on the shelf at most auto parts stores or have next day from the warehouse.

 

I understand thank you I’ll be buying a new one . another question how do Ik if I have, Manual or power breaks I honestly can’t tell if I have Manuel or power. my master cylinder has 2 bowls it’s connected to a break booster the proportioning valve has a wire like thing in the middle of all of the break lines, I can send pictures tomorrow in detail because if I have manual breaks wouldn’t I have to use every once of my leg strength to do a casual stop? Because that’s what it feels like

 

That should be power brakes if it has the booster,easy to tell if you get on a hill put it in neutral and coast downhill with the motor off and step on the brakes,if the motor is off you won't have power to the booster and you'll have to push the pedal really hard to get any brake action. lol
Start the engine and your brakes will be back to normal.
By 1976 I think they all had power brakes but don't quote me on that.

 

ima end up with failed breaks and a crashed car 😂I’m pretty sure I have power breaks because it was normal when I first drove it then it started getting hard might just need to be bled and replace the master cylinder

 

Has the car been sitting? Maybe you should get the brakes checked by a pro. You could have moisture in the lines or the flexible hoses are aged and at starting to come apart internally or dry rotting. Changing parts is one thing; making sure a 47 year old car is safe is next level. Keep in mind when these cars where design to last 8-10 years. They came with 12 month warranty and banks would only finance them for 3 years.