Problem with removing ABS. Which Master Cylinder to use?

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I have a 96 Legacy Outback that I decided to take the ABS system out of to give me more control and make space for a auxiliary battery. Couple years ago I swapped everything over from a 91 Legacy to my 99  Outback wagon and it worked but the pedal has always felt like there was some air in the system. I bench bled it twice and bled the car a million times and nothing improved it. I figured it was just the rubber lines expanding or something and have lived with it ever since. Today I was switching everything over from a 93 to my 96 outback when I noticed that the size of the bore is stamped on the master cylinder. Turns out my Outbacks come with a 1 1/16 inch bore and the Legacys come with a 1 inch bore. I believe Legacys have 1 piston calipers and the Outbacks have 2. So my questions are:

1 Do you think that the 1/16 inch bigger bore makes the difference and would give me a hard pedal again?

2 If so does anyone know of any 1 1/16 inch Subaru Master Cylinder that has the same line locations as the one in the picture?

If not  then maybe a master cylinder with lines in all 4 locations and I'll just plug one.

I've seen about 5 different combinations of Master cylinders on Legacies and Outbacks so I hope there's the right combo out there.
I have a hill holder so one line goes there.

My 0utback Master Cylinders have just the 2 side ports and not the bottom so I guess my last resort could be to have someone tap that bottom left port for me. They would also have to press in the brass piece that the brake line flange bottoms out on. I'm not even sure who would even do that here in Colorado. Any help would be great. Thanks

[Fairtax4me]

I looked into something similar to this a few years ago and kinda gave up after reading about all the differences in master Cyls, brake calipers, proportion valves, hill holders, and how many different combinations of them there are. Change any one peice and you change pedal feel, stopping power, and possibly the F/R balance of the brake system.

 

Larger bore in the master cylinder = more fluid moves when you push the pedal. Moving more fluid causes you to lose some of the mechanical advantage of the hydraulic system, which equals more foot effort to get the same pressure. You basically have to push harder to get the same stopping power, and the pedal will not move as far.

 

Smaller MC bore moves less fluid, but it increases your mechanical advantage, so less foot effort creates the same pressure. Pedal will move farther, and you will not push as hard to move it.

 

Where that makes the next difference is at the caliper end. A dual piston caliper generally requires more fluid, but less pressure to get the same stopping power. The fluid pressure is spread over a wider surface area on the back of the pistons, which means the pistons push a bit harder. If this were paired with a small MC bore, the brakes would probably feel a little soft, because you have to push the pedal farther. Or if paired with a much smaller MC bore, the pedal travel may be too long, meaning the pedal could hit the floor before you get full braking power. But I think you would have to switch from a 1-1/16 to probably a 7/8" or smaller MC to get that much effect.

 

I would think you can safely switch from a 1-1/16" to a 1" bore without too much issue. You'll feel the pedal is a bit easier to push, but the travel range should still be within an acceptable limit.

 

Search around on rockauto for master cylinders for various years and models. You'll see there are different bore sizes and port layouts depending on model, ABS, or non-ABS, and hill holder vs non-hill holder.

Generally with the 95-99 legacy a non-ABS MC would only be used with rear drum brakes. There may be a 90-94 legacy with disc brakes and non-ABS, but I'm not sure.

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Looks like a 91 to 95 non abs front wheel drive SVX will work. It has 4 ports and 1 1/16 bore so It would be identical to the stock system if I plug that bottom back port. Problem is that car is RARE with that setup and not even the dealer stocks it.