This vacuum booster has an 8" dual diaphragm. It is meant to be a direct replacement for F350 trucks and a direct bolt in upgrade for F250 and some half ton trucks. The optional master cylinder has a 1.25" bore and ports on the driver side, away from the engine.
These boosters are not made with original tooling. They are very high quality built with modern 21st century tooling. They are functionally identical but they have a slightly different appearance than an oem booster. This has no effect on performance. The snout on the back side of the booster does NOT fit within the oem plastic sleeve that goes form booster to firewall opening. You can cut your oem sleeve down slightly for clearance, or remove it. The boosters come with a flexible rubber seal that goes in this same location but it is not long enough to make contact with the firewall. This does not affect the cantilever style trucks.
Ford had three major types of boosters form 1968 to 1979. They had two main differences- the rods that connect to the pedal (or in the case of the cantilever trucks, to a lever), and also they accepted very slightly different master cylinders. I have created one booster that works in all three applications. I have done this through the use of threaded detachable rods as you can see in the pictures. This is a great feature becasue it provides slight adjustability in the rod length and it significantly reduces the chances of damage during shipping.
Here are pictures of the original booster types for reference:
The other difference in F350 brake boosters across the three styles was that they accepted two major types of master cylinders. the biggest difference was the diameter of the portion of the master cylinder that is inserted into the booster. These boosters only accept 1.5" +/- .1" diameter master cylinders. This diameter is not to be confused with the bore size, that is something entirely different.
F350 trucks seem to have come with a 1.000", 1.062" or 1.25" bore master cylinder. While there is no absolute need to use these boosters with a larger bore master cylinder, I highly recommend it for everything but cantilever applications. The larger bore master cylinder gives a much better pedal feel. All things the same, a larger bore master causes less fluid pressure from the same force on the brake pedal. The larger boosters overcome this mechanical disadvantage just fine and the end result is not only more fluid pressure than an F250 booster, but significantly more fluid volume.
I offer 1.25" bore and 1.062" bore master cylinders with these boosters. They can be used with either disc/drum or disc/disc. I have not tested this with cantilever trucks yet. The 1.062" bore maters work well with cantilever style boosters and single piston caliper. The 1.25" bore masters work well with everything else, but also they do work well with single piston calipers too and result in a little less brake pedal travel.
Drum front brakes- This booster and master can work with front drums but it will be borderline too powerful. Front drums are prone to locking up unintentionally when a larger booster powers them. A medium amount of force on the brake pedal will have the feel of heavy braking. The 1.25" bore master is a good idea and has the effect of slightly reducing fluid pressure compared to a 1.0" bore master.
OEM part numbers this is intended to replace for reference:
1976 and older long straight rod: D6TZ2005H
1977 and 1978 cantilever: D7TZ2005D
1979 angled/offset: D9TZ2005A / D9TZ2005E
The large bore master cylinder oem number is C9TZ2140G which is original to 1968 to 1975 F350 and some F250. But this works well with really any applicaiton other than front drums.
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