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1954 GMC 350

Discussion in 'The Antiquated' started by TimCT, May 19, 2020.

  1. TimCT
    Joined: Jun 6, 2017
    Posts: 169

    TimCT
    ALLIANCE MEMBER

    Hey Guys,

    I finally gave in to my truck roots and pulled the trigger on a 1954 GMC 354-27. Former fire truck from here in CT, its a flatbed now. Being that 1/2 tons are going for crazy money, a 2 ton truck is what was in my price range.

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    This is the cleanest AD truck I've seen in person - cab corners, kick panels floors, all super solid with zero rot. 18,000 original miles, which I believe to be original, judging by the fan belt.

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    The frame has been shortened about 40" when they took the pumper body off and replaced it with a flatbed. Looks like they welded the frame, but also doubled it up on the interior and bolted it all together. The wiring is all hacked - I was told by the PO that one of the other POs started a 12V conversion. Apparently as far as they got was removing the original parking lights and trim and bolting on some cheesy little trailer lights, and hooking them up to nothing. Same with tail lights. I'm planning on keeping it 6V for now at least, though I haven't started tracing wires yet.

    I've noticed a couple odd things about it - the hood isn't original, you can see the ghost of the 300 emblem under the GMC emblem, and the green paint under the red also doesn't look right. Also, I think an effort was made to add some sort of extra patina - the brown paint around the cab corners and elsewhere, it looks like it was 'splattered' on the wheels, as well. The whole grill was taken off the truck so they could paint the grill surround an off white and leave the grill itself chrome, and then everything was put back together with about half of the required bolts, most of which were still loose. I guess stuff like this is par for the course for something over 65 years old.

    Still, tons of originality. Working hydrovac, a PCV system, the vacuum shift 2 speed rear works (I'll need practice), I love the GMC script on the rear axle.

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    The 270 doesn't run great. It would start right up, but idle quality wasn't great and it would fall flat on its face when you hit the gas. I ordered a kit and took the old Zenith apart, and found the steel accelerator pump cup seized to the carb body, so that added about an hour to my carb reuild time, digging the old cup out.

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    Drained the old gas out of the tank and replaced with fresh, and also cleaned the old gas and rust out of the screen and glass bowl on the fuel pump. It had sooty R43 plugs in it which sounded way too cold to me for a truck that's not going to be doing much hard work any longer, so I put in new R45s and fired it back up. Again, starts right up, but idle quality isn't great. I need to put a vacuum gauge on it and dial it in. I did take it down the road and it drives much better, it accelerates now with a functioning accelerator pump. Adjusting the valves is also on the list for this weekend, as well as checking everywhere to see if there is a vacuum leak. I checked around the manifold, and all the vacuum connections for the PCV and the hydrovac, but I didn't check at the wiper motor, or down at the hydrovac, or anything to do with the 2 speed rear. I can hear it sucking air at the carburetor - where the accelerator pump shaft goes through the carb body. Is that normal, or should it seal better?

    Anyway, I'm very happy for the new Antiquated section, so I can share this one with the HAMB. I'm sure that once I get the 270 running like a sewing machine, I'll be looking into multi carb setups and headers and ditching the governor...but I'm getting ahead of myself. For now.
     

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  2. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,245

    jimmy six
    ALLIANCE MEMBER

    Have fun, the rocker cover looks to have the correct fittings but I didn't realize a 54 would have a PCV system other than military sealing. Is there a valve anywhere on the engine? I see it still has the governor under the carb, it can be the source of air leaks. A 2speed rear is fun to split between gears when electric. I loved to do it when others riding along couldn't figure out what I was doing...Big project.good luck.
     
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  3. TimCT
    Joined: Jun 6, 2017
    Posts: 169

    TimCT
    ALLIANCE MEMBER

    Thanks @jimmy six . There is a PCV valve, though not like one I've ever seen. I took it off when I was rebuilding the carb to clean it out, and found it to have a 1/8" hole drilled through the middle - I could see daylight from one end of the valve to the other. It didn't hold vacuum in either direction. From what I hear, that's how they're supposed to be? They had a bad habit of loading up and sticking, so the hole was to combat that.

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  4. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,245

    jimmy six
    ALLIANCE MEMBER

    Early PCV valves were kinda like a calibrated vacuum leak. I believe a 65 Corvette had just a hole in a fitting. If yours still has a road draft tube it would “leak” thru there but I thinks yours oil filler on the right side is sealed. I was just trying to help with the rough idle and air leak sound.. have fun..
     
    tractorguy likes this.

  5. TimCT
    Joined: Jun 6, 2017
    Posts: 169

    TimCT
    ALLIANCE MEMBER

    Thanks @jimmy six , I think that's probably how this one operates.

    I do have the sealed oil fill on the other side, with a little breather cartridge filter on top of the fill tube.
     

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