So this is a lesson in not to skimp on the brake components. I pretty much replaced the entire brake system, including lines and hardware on my 51 thinking that the master cylinder was in an okay shape. But sure enough, I developed a sponge brake pedal and noticed the leak on the plunger side of the cylinder. Bummer...

So when I was looking at the usual vendors for the part, I noticed that there are 2 options. Stock and 1 1/16" Bore version... So my questions are...

1. What is the stock bore size?
2. Why would you use one versus the other?

Thanks in advance for the input.

 

I don't have the shop manual with me. But I THINK I remember that the "stock" one is 1 inch. It's used on the half ton trucks. The larger one is for the larger trucks. Somebody will correct me if I'm wrong.

Psssst.....you can buy a refurbished MC at Napa, Advance, Carquest, etc. a whole lot cheaper than the catalog places. It's one of the few things that you can actually order at a regular parts house and usually have it the next day.

 

From what I learned on the HAMB board when researching information on MCs for my '37 Buick, you want to use the same size bore MC. Too big and you'll have a hard pedal with little movement.

I'd also recommend NAPA, for a F-1 or F-100 they'll either have it or get it for you the next day. I have also had pretty good luck with parts for my F-2.

 

Just a little more info on master vs. slave cylinder sizes:

A larger master cylinder piston will generate LESS hydraulic pressure in the system at the the same foot pressure than a smaller piston, but will move MORE volume and consequently require less pedal travel to achieve pressure than a smaller piston. Of course, the exact opposite conditions are true for a smaller piston vs. a larger one. It is fairly common for car/truck builders to fine tune their pedal travel and feel by going to a different master cylinder bore size. You can often have an existing cyinder overbored to run a larger piston or sleeved to run a smaller one also.

Wheel cylinder and calipers work the opposite direction. A larger caliper or wheel cylinder bore and piston size will generate more apply pressure and require more fluid volume to operate than a smaller one. You can use this to your advantage if you're trying to balance a non-stock brake system. Many wheel cylinders are interchangeable other than bore size and the direction that the line enters. If you have problems with your rear brakes locking up well before your front brakes, you can swap to rear cylinders with a smaller bore and reduce the applied pressure.

 

Thanks for the info everyone. I checked with Napa and they can have one in a day or so. Although it is a few dollars more expansive at Napa, I think I will go that route for the convenience sake.

 

I'd rather go through NAPA, or a local dealer whenever possible even if it cost a little more. If there is a problem it's a lot easier to grab someone in person and have them make it right than have to deal with the hassle of shipping parts back and forth.

I have found NAPA usually is cheaper than mail order places or the two local Ford reproduction parts dealer I have in the state, one is about 20 miles away. When I redid the brake on my F-1 panel I was able to get 3 of the 4 wheel cylinders at NAPA for around $12 each. I was in a hurry and had to get the fourth one from one of the repro parts dealers for $21.

 

1939/47 'Commercial' & 1948/52 F1 & 1953/56 F100 = 1"