Chevrolet 1533X2 30-cwt trucks

[Grant Bowker]

Following the discussion of how and where the outlet was mounted on MCP, I recently came across a through-frame outlet on a Chevrolet CMP frame that was being prepared for scrap. Don't cry, the frame really was beyond help. (heavily delaminated, shortened, non-standard wheelabse, bent, abused....)
The photos show where it was located on the CMP frame (between the left-hand step brackets) and the fitting. One end is shaped to take a standard 45 degree SAE (single) flare (see photo of mocked up 5/16" tube), the other is threaded similar to a schraeder tire valve stem. Although rusted, it looks to have been threaded both outside for a protective cap and inside to suit a valve core. I don't understand why they would have put a valve core here as any hose to inflate a tire would have had to incorporate a device to press the core open - otherwise the pressure from the pump would keep forcing the core closed so no air would flow. (and the core would restrict flow...)

[Grant Bowker]

More photos, inside of frame view and the fitting.
For those who are curious, the outside of the part that passes through the frame is threaded 1/2-20.
I believe the fitting is described as "connection assembly, tire pump frame" in the parts list which would make it part number 1799265 which doesn't have an asterisk* as a unique to CMP. But, I don't see that part number in the Chevrolet Master parts list 1929-1948....

[Grant Bowker]

More, to show the assembly to line...

[Lynn Eades]

Grant, I would suggest that is an inlet rather than an outlet?

[Grant Bowker]

I won't say you're wrong, but in the photo above (#218 from Colin) I'm convinced the inlet is the inverted triangle shape (or the air cleaner in the diagram) and the output is the hard (copper in the parts listing) line from the pump cylinder head heading toward the outside/left of the truck. Similar on both CMP and MCP that leads to either the through-frame fitting on a CMP or the running board fitting on MCP (see post #209). I don't see a reason to extend an inlet for the pump to the outside of the vehicle but you would certainly want the outlet for connection of a hose for tire inflation to be on the outside. MB-C2 supports the hard line being the outlet as does the structure of the ball check valve below the fitting for the hard line.

[Charlie Down]

Hi Grant and Lynn,

I must admit that I was under the impression that the triangular fitting, later replaced with the filter, was the inlet, and that the coiled copper tube connected to the frame, and outlet nozzle and airline. The opposite set up doesn't make sense to me, (but I've been wrong before)! However I don't think so this time.