help, whats the deal with my brake master cylinder year

[Catfish28]

OK. I'm confused.
I'm rebuilding a 78 and am to the point of rebuilding my brake master cylinder. I assumed it was original and correct for the year truck. I cleaned it up and ordered a master cylinder piston kit. PIc attached of the MC. The odd thing is my bore is 1". I didn't realize it until I ordered the cylinder kit that my year with front discs should be 7/8" bore. So I have 04493 60040 rebuild kit which is 7/8" and my bore is 1". I understand that 1" dual reservoir master cylinders were for all drum brakes and ended in 75. But this cylinder look exactly like a 76 through 80 MC with the port locations, etc. It is an OEM MC. Stamped on the sides are 52, YC, and ASCO.
Any insight? Thanks in advance.

 

[zebrabeefj40]

Might have been previously rebuild and overbored to 1" in the process. Or it's from a non-USA truck. IIRC they had drum brakes into the early 80's.

Nick

 

[Catfish28]

Thanks. So I suppose I'm in the market for a new mc. Another question. Would the brake booster be different for the 2 different bores?

 

[zebrabeefj40]

The booster will work with either disc or drum brakes.

Nick

 

[Tysano]

If you can find a 1'' rebuild kit, just rebuild it and run it.

 

[cult45]

I wouldn't run a drum/drum master on disc/drum brakes. The bore size and length is specific to drum/drum; also disc/drum; also disc/disc. Find the correct master and install it. What you can do is run an early 80 series disc/drum master and booster [non ABS] as an upgrade. The booster requires turning 180* and a small spacer IIRC, but if not then you can also run an early 80 series master on a 40 series booster. Several friends have done so and they say it's a great upgrade.

 

[cuencanolenny]

Interesting information. My 1979 FJ40 is non-USA. I live in Cuenca, Ecuador. My brakes are drum all around, but the front brakes are larger diameter and wider than the drums on my 1970 FJ40. Presumably they are FJ45 brakes as that was a heavier vehicle and perhaps this use was a Toyota way of improving brakes without putting discs on the front. However, my master cylinder does not look anything like the one shown above.