Hello James, just a thought. It looks like your new master cylinder is not pushing out a sufficient amount of fluid out to the brake cylinders because of the smaller 1-1/8” bore.
If you work out the volume of your old master cylinder and then your new one, there will be a difference.
That difference will relate to pedal movement, it maybe the case that you are running out of pedal before the wheel cylinders lock against the drums.
If you can adjust your brake shoes to take up the slack in the wheel cylinders, your new master cylinder will then have less fluid to push out.
Your old master cylinder can push more volume being 1-1/4” in diameter. I feel there is nothing wrong with the brake system just the volume of fluid displacement of your new one.
To recap, take out the slack at the brake cylinders. Then bleed again to see if you get a pedal.
It sounds like one of those , let us know how you get on, just a thought
Hello James, just a thought. It looks like your new master cylinder is not pushing out a sufficient amount of fluid out to the brake cylinders because of the smaller 1-1/8” bore.
If you work out the volume of your old master cylinder and then your new one, there will be a difference.
That difference will relate to pedal movement, it maybe the case that you are running out of pedal before the wheel cylinders lock against the drums.
If you can adjust your brake shoes to take up the slack in the wheel cylinders, your new master cylinder will then have less fluid to push out.
Your old master cylinder can push more volume being 1-1/4” in diameter. I feel there is nothing wrong with the brake system just the volume of fluid displacement of your new one.
To recap, take out the slack at the brake cylinders. Then bleed again to see if you get a pedal.
It sounds like one of those , let us know how you get on, just a thought