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Hot Rods Cool score....GMC 302 Military

Discussion in 'The Hokey Ass Message Board' started by Jethro, Sep 1, 2018.

  1. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    I haven't started a thread for a while but can't wait to tell about my latest score.
    I was perusing Kijiji as usual between sips of coffee and came across an ad that just said "302 military", no picture just a picture of a handwritten note that had some casting numbers and descriptions. I called the guy and he described it as a crate motor that had a paper military tag on it that said 302 and had a metal rebuilders tag on the block that said bore .030 , throws .010 . mains .010 and the machine shop name.I went to look and it indeed was a military 302 in a crate on a heavy angle iron cradle with all the attachments. 28 volt sealed generator , 24 volt sealed ignition and air compressor all painted beige/grey.
    I struck a deal and it came home with me.
    Going into the Model A 33.jpg
     
  2. tubman
    Joined: May 16, 2007
    Posts: 5,912

    tubman
    ALLIANCE MEMBER

    Good score! I've always wanted one of those. From the looks of it, is it a fresh rebuild? What kind of a carburetor has it got? (It kinda looks like a early Mercury or Oldsmobile.)
     
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  3. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    It was a fresh rebuild in 1984 so says the tag. The carb is a 2 barrel Holley with a governor that is somehow linked to the distributor by copper lines. The ignition is a self contained watertight 24 volt system with braided steel covered wires and special waterproof spark plugs. Been doing some reading on the Inliners site and they are slightly different from the civilian but able to be adapted with a few small modifications.
     
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  4. bct
    Joined: Apr 4, 2005
    Posts: 3,103

    bct
    Member

    your injection going on it?
     
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  5. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    Y' never know.....but now that I have a bona fide "old school" motor I might have to go all Trinity Valley on it:cool:
     
  6. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,029

    302GMC
    Member
    from Idaho

    Check casting dates - most of these are 1953 - 1955 built & have one of the best cylinder heads GMC cast. The ports need no work, 1.94 Chev intakes & 1.60 Pontiac exhausts fit after going to 45 degrees seats. If the rebuild was done by the army, I'd want to tear everything apart they touched. I've done 4 of the heads from army 6x6s with no hours, and found 1 milled half way across, then they went to lunch … some with guides installed with shim stock. They didn't do much better grinding cranks, either.
    The block in a heavier casting than the civilian - some work on the starter might be needed to clear. The crank is 7 lbs. heavier than a 270, & you should have a steel camshaft - the re-grinders don't care much for cast cores.
    The best part of it all - once the engine is stripped to the basic block/head/pan, everything from Chev - GMC civilian engines fits. Only the water pump is GMC only.
     
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  7. T. Turtle
    Joined: May 20, 2018
    Posts: 214

    T. Turtle

    It's probably from a GMC M135 which I think always had the 302s. I'm surprised why people never mention them when they talk about the 302 - GMC made thousands of the things and (last time I checked) you can still find them for not TOO much money. But maybe there's something I'm missing like very low compression etc.
    [​IMG]
     
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  8. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    Worked on plenty of those when I was in the Army. I used Stainless valves made for Chevy V8 heads. But in the +.100 length. Over the counter item. As I remember stock length was short. Mil spec engines have no provision for a fuel pump. Electric as delivered. Mounts are on the side of the block. I used them interchangeably in my Bonneville car with commercial blocks.
     
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  9. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    I'm slowly taking it down to bare bones...It looks like a regular machine shop did the work not military so maybe OK. Still going to take it apart to check things and replace gaskets.
     
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  10. Deucedreamer
    Joined: Jan 11, 2010
    Posts: 542

    Deucedreamer
    Member
    from BC Canada

    That’s looks like a great engine!! Nice score. I put a 302 gmc in my 40 Chevy pu. It started as a military engine and I used civilian internals and a civilian head. The military engines have bosses on the front on the sides for mounting PTO’s etc. They work great for motor mounts if you don’t want/can’t use the saddle mount, which is what I did.
    536B3D03-0381-4DCC-91B8-EDADA0FFD2A9.jpeg .
     
  11. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 27,740

    Jalopy Joker
    Member

    Congrats - rarely have used Kijiji for searching for stuff - have get back to it
     
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  12. RichFox
    Joined: Dec 3, 2006
    Posts: 10,020

    RichFox
    Member Emeritus

    I bought one Ordnance rebuild from the Renton Wash, station. It was a great engine. Nothing wrong with it. All cylinders had been bored and sleeved to standard. Everything inside seemed new. Don't know the story on 302GMC's engine. I understand all 302 cranks are heaver than 270 cranks. I used a 270 crank in my best GMC. Rod journals ground to Pontiac size and 5/8 long Crower rods.
     
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  13. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    Well , it feels nice to be re-ignited again. Going to Speedweek lit my fire to build a hot rod.
    So, after taking some of the externals off the Jimmy I spied an intake on my shelf that I bought for a 292. Just for laughs I held it up to the intake ports and it was close to fitting. I ground the flanges a little and it bolted on. The ports don't quite line up so I am going to try and cast some adapters to go from rectangle port to round port. I made a plug for the casting and a plug for the core. I'll document this adventure on another thread.
    I also whittled a couple of valve cover nuts to replace the old steel ones. And I filled in a breather hole that was drilled into the cover. Oh and I modified a 250 distributor to fit too.
    I guess I've been busy....feels good to be back in the shop! P1010005.jpg P1010009.jpg P1010010.jpg P1010006.jpg P1010008.jpg P1010011.jpg
     
  14. typo41
    Joined: Jul 8, 2011
    Posts: 2,572

    typo41
    Member Emeritus

    You want to give a list of the ones for not too much money,,, the last best deal I found was a locked up one for $400 and they average around $1100 around here for a unbuilt grease hunk of metal. We put a 350 Chevy into our formally GMC powered LSR roadster cause we couldn't find/afford a 302. But thanks to a fellow club member that was thru with his 302 (got all the records he wants) we will have one for future LSR.
     
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  15. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,295

    jimmy six
    ALLIANCE MEMBER

    Looks like it still has a military 2 piece pan from the 6by. The oil pump is the same but will need a different pick up if you put on a different pan for clearance in a hot rod. I would use a 228/248 for a street engine and I used one racing too. The military pan makes an excellant frame since it's double wall at the rail to make a new pan from.
     
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  16. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    About that, can I just take the extension off and fab a plate to cover the bottom of the pan? Oh and use a different pickup
     
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  17. sololobo
    Joined: Aug 23, 2006
    Posts: 8,254

    sololobo
    Member

    Does it have the huge oil filter? We had one in our group out of a military rig with the super big oil filter. Love these mills, best wishes on your build. 6 in a row is a cool way to go!!
     
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  18. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    What do you consider 'huge" the canister it has is about 2 quarts. I'm going to convert to full flow eventually.
     
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  19. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,029

    302GMC
    Member
    from Idaho

    " The last best deal I found was a locked up one for $400 and they average around $1100 around here for a unbuilt grease hunk of metal. ''
    Are they really that hard to find ? I'll run another Korean War 302 thru the classifieds ...
     
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  20. oldsman41
    Joined: Jun 25, 2010
    Posts: 1,556

    oldsman41
    Member

    What are you planning to put it in? It will be killer in anything Chevy.
     
  21. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    Planning on a Model A coupe....there's a black Chevy coupe with a Jimmy that is just killer!
     
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  22. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

  23. typo41
    Joined: Jul 8, 2011
    Posts: 2,572

    typo41
    Member Emeritus

    Let me know and I'll send the $500 up, cause they are not expensive and easy to find like a SBC's
     
  24. LAROKE
    Joined: Sep 5, 2007
    Posts: 1,974

    LAROKE
    Member

    Welcome to the Jimmy engine club.
    [​IMG]
     
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  25. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    Thanks for having me!
     
  26. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    So , here's where I am today. I finally tried my hand at sand casting some aluminum. I made up my mold and core mold and ordered some petrobond off the internet. I cast three adapters that transition from a 292 rectangle intake port to a 302 round intake port. The 292 ports are spaced at 8-3/4 " centre to centre and the 302 are 9" c to c. The out board adapters had to be moved 1/4 " past centre to mate with the 302 ports. I'm going to grind where the port overlaps and port match the adapters to the manifold.
    I am going to create a tech thread that documents my casting adventure....stay tuned! 1 - 1.jpg 2 - 1.jpg 3 - 1.jpg
     
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  27. edgeabilly
    Joined: Dec 10, 2006
    Posts: 735

    edgeabilly
    Member

    Had A 292 Chevy but always wanted a Gmc302 cause of that fing 32 Chevy above.. :)
    Still looking. Internet search engines are not as good as they use to be.
     
  28. hillbilly4008
    Joined: Feb 13, 2009
    Posts: 2,918

    hillbilly4008
    Member
    from Rome NY

    20181031_165152.jpg Subscribed. I also just picked up a military 302 fully rebuilt.

    Will be watching to see how you convert it all over.

    I have the same question about the double pan. Why couldnt you just remove the bottom pan, cap it off, then shorten the pickup?
     
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  29. Jethro
    Joined: Mar 5, 2001
    Posts: 1,618

    Jethro
    ALLIANCE MEMBER

    I took the small pan off and shortened it to about 1-1/2 deep .I had to machine an adapter to make the pickup work. the military oil pump has a different bottom than a civilian . When you take your pan off you'll see that the front of the pan has a kind of cut out probably for clearance. It takes some volume away . the military pan is super heavy duty. The rails are reinforced and it seems to be a real heavy gauge.
    I just ground off the "bump" so I can use a 235 starter. I picked up a 235 bell housing and starter from a friend off a 59 Chevy car ,fits like it was made for it.
     

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