I purchased this project as a 1940 KC ½ ton pickup. It turned out that it is a ’40 cab on a later chassis (’46-’47?).
I have been reading up on Huck brakes and have ordered the Herbrand 188 tool to make it easier to work with the springs and not get too frustrated. While I wait for the tool to be delivered, I inspected the brake lines and they do seem to be true to the “story” that came with the project - that the brakes had been redone. (The lines I have inspected so far appear to be unused!)
I went through my stash of parts and put my hands on the master cylinder I purchased from the Barry Weeks auction. I believe that it is probably an appropriate unit for this ½ ton truck, but if someone could confirm that from the casting or part number on the unit, I would really appreciate it! (This unit does appear to have been rather freshly rebuilt.) The casting number on the unit is 5450256-15-R, there is a “Model” stamped into the end of the unit, “Model No. 325-J” (I do find the casting number 5450256 (with no following dash numbers listed in the ’29-’50 Master Parts catalog for 1936-’37 with a note, “(does not have 11/32 hole thru cyl. wall)”. It is also listed for 1938-’46 All ½ ton Comm, with a note, “(has 11/32 thd’d. hole thru cyl. wall”). Does anyone know what the 11/32 hole was for? I have not located it in the drawings, so I don’t know where to look to see if it exists in the unit that I have.
I was disappointed to see that there are parts missing from the master cylinder. I am new to this, but it appears that I am missing a spring, a valve, a valve seat and probably a gasket for the end plug. Is there a source for these parts or will I have to locate a rebuilt master cylinder? Included in the lot from the auction were a bunch of brake parts, including a couple of springs…but I don’t know if they are the correct springs for this master cylinder.
The master cylinder does seem to bolt correctly to where it should.
Again, I am learning as I go along, having not dealt with this sort of thing in 59 years when building a hot rod as a young guy. So the gaps in my knowledge and experience are huge!
Last edited by klhansen; 04/05/20267:18 PM. Reason: fixed title spelling
Nick 1940 KC Model 1/2 Ton Pickup Project (with '37-'39 Bed and what we think is a '42-'46 Frame) Taos, New Mexico
Nick, That is the same MC I have on my 1940 with a couple of exceptions. You are asking about the 11/32" hole. Mine has that and it is for the brake light contact/sending unit. You can see this in the pics attached. The other exception is the numbers on the end cap. Mine has an A instead of the J yours has. Not sure what that indicates so I apologize for that. Just wanted to point it out. They look very similar. By the looks of things, your MC seems to be complete. What parts do you feel you are missing? The spare parts all appear to be for wheel cylinder rebuild and retainer springs for the Huck system. There are 2 springs pictured that "may" be for the park brake lever extension inside the rear drum. Hard to tell, but since they are in with brake parts and I happen to be missing those myself they caught my eye. I have included some pics of a rebuild kit for that MC that I purchased and found I could not use due to the condition of my MC. Look at those to confirm "if" you are missing anything for the MC you have.
Brendan 1940 Chevrolet 1/2-Ton Pickup Restoring Dad's old truck In the Gallery Forum
I am significantly more confident now that I will be able to make this master cylinder work.
Brendan, did you end up using the rebuild kit? If your MC was not in rebuildable shape and you have the kit as excess, let's talk.
Also, if there are parts in that pile that you need and are excess to me, we should talk about that too.
Knowing that the 11/32" hole is for the brake light switch makes sense.
One thing that I am concerned about is the end plug. The MC I have came with a copper washer between the end plug and the body of the master cylinder - but the ID of the washer is greater than the OD of the plug threads...and the illustration from the shop manual doesn't appear to show a washer there at all. It appears from the photos of the rebuild kits that there is a rather large ID washer of some type that comes with the kit. Is it for the end plug or somewhere else?
Nick 1940 KC Model 1/2 Ton Pickup Project (with '37-'39 Bed and what we think is a '42-'46 Frame) Taos, New Mexico
