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Gmc 305 v6?!?!?

Discussion in 'The Hokey Ass Message Board' started by blown240, Dec 26, 2010.

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  1. blown240
    Joined: Aug 2, 2005
    Posts: 1,814

    blown240
    Member
    from So-cal

    I am looking at possibly buying a 66 GMC truck with a 305 V6 in it. I didnt even know this motor existed. Are they any good? What can you tell me about them. THANKS!!
     
  2. newsomtravis
    Joined: Jun 1, 2009
    Posts: 562

    newsomtravis
    Member
    from pville, ca

    big ass slow torque monster......think big block deisel v6...i know it runs on gas.....but revs like a diesel......
     
    travis.vermeulen likes this.
  3. lot's of torque, very durable, not the best fuel mileage.
     
  4. That just about covers it.
     

  5. boat anchor!
     
  6. Mark Karger
    Joined: Feb 22, 2005
    Posts: 397

    Mark Karger
    Member
    from houston TX

    I had one in a '60 GMC 1 ton stake bed. It could pull a building off it's foundation, but loved gas stations. Really heavy engine. with large, thick pistons which do not like to rev. Massive lower end hard to blow up. An attractive engine with odd head/valve cover shape.
     
  7. burnout2614
    Joined: Sep 21, 2009
    Posts: 612

    burnout2614
    Member

    I agree with all of the above except boat anchor. Only because that motor is so heavy it will sink most boats! peace
     
  8. harpo1313
    Joined: Jan 4, 2008
    Posts: 2,584

    harpo1313
    Member
    from wareham,ma

    i had a 63 and it had plaid valve covers,couldnt get it to run smooth .found out later they were all like that,screwy firing order if i remember correctly.
     
  9. Dadstoy 2
    Joined: Nov 20, 2010
    Posts: 245

    Dadstoy 2
    Member

    We once had a big ole 59 GMC wrecker with that engine in it. Got a ticket for going to slow on the interstate while pulling a school bus.
     
  10. My dad had one in his '63. Had over 300,000 miles before he even had the valve covers off. Don't remember it being hard on gas but back then who cared?
     
  11. bob308
    Joined: Nov 27, 2009
    Posts: 220

    bob308
    Member

    the only thing thats makes them worth anything is the price of scrap is up.
     
  12. povertyflats
    Joined: Jan 8, 2007
    Posts: 8,282

    povertyflats
    Member
    from Missouri

    I had one in a dump truck a few years ago and if I remember correctly it held 9 quarts of oil.
     
  13. rjaustin421
    Joined: May 1, 2009
    Posts: 337

    rjaustin421
    Member

    If the truck is in nice shape I would grab it as IMHO that body style is the best one GM has ever designed or will ever design.

    Bear in mind if you decide to repower it the base V/8 engine for that year weighed 795 lbs and you would be looking at the sun & rattling yer' kidneys with a typical V/8 with the stock front springs.

    Buy stock in Shell Oil.
     
    Last edited: Dec 26, 2010
  14. Woogeroo
    Joined: Dec 29, 2005
    Posts: 1,226

    Woogeroo
    Member
    from USA

    The 6066 GMC Guy



    Scroll down the page linked above, there are lots and lots of tech articles about those trucks and engines to read on that site. That will help you make a informed choice.

    If you want to use the truck as a TRUCK, then it is a good engine I've been told by people who have them, with lots of torque as others have stated. They were big gas hogs, but consistent gas hogs I've been told.

    That same engine was used by GM for stand alone applications... for generators, various type of pumps and things as well.

    -W
     
    Last edited: Dec 26, 2010
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 55,935

    squirrel
    Member

    The larger versions of the engine (401-478) are decent mills for heavy vehicles. The 305 is a turd. I recently dealt with 3 of them....they're all gone now, good riddance. I did get a bit more than scrap value for two of the engines (in pieces) from a GMC nut.

    If the truck is in good condition, and the engine is quiet and runs good, and it's priced right, then it might be worth buying. Don't expect to get good gas mileage or much performance from it.
     
  16. Unibodyguy
    Joined: Dec 23, 2007
    Posts: 403

    Unibodyguy
    Member

    Had a 65 GMC semi tractor that had a 401 in it with 5X4 trans. pulled real good but could never pass a gas station.

    Michael
     
  17. gas pumper
    Joined: Aug 13, 2007
    Posts: 2,957

    gas pumper
    Member

    I have one in a 6500 69 GMC. It's a bucket truck and chip body, kinda heavy. But it will get around town and idle all day longrunning the PTO without missing a beat. It will last forever. It had an odd stromberg on it and now has a Rochester 2GC. If you just gonna put around town it's great.

    A guy I know had one in a 3/4 ton PU and it was more than enough for that with a granny 4 speed.

    Solid lifter engine. PCV's are under the valve covers and screw right into the intake runners. kinda unique.
     
  18. F&J
    Joined: Apr 5, 2007
    Posts: 13,222

    F&J
    Member

    I agree they are durable but not good on gas, and they like lower RPMs.


    One thing worth mentioning about the 66 GMC truck 4 speed if that's what you have; I ran across a guy who has one, and he told me that it was NOT a granny first gear and that you had to start off in first gear.

    I was sure he was wrong until I drove it. It really was a driveable first gear with a nice spread in ratios between all 4 gears. I have never heard or seen another one like it since. I wish I had taken ID numbers off of his trans because it was so nice to drive.
     
  19. blown240
    Joined: Aug 2, 2005
    Posts: 1,814

    blown240
    Member
    from So-cal

    Thanks for all the replies. The one I am looking at needs a tune up and a battery, but other that that it runs and drives like it should. Its a 4 speed and I would really like an auto trans in it. I am buying it as a fun family round town cruiser, that can double as a Home Depot runner / parts hauler.

    The price is right, but it sounds like I may have to do a full drivetrain swap to make it what I really want.

    I wonder how hard it would be to get a th350 and a super tall gear behind it. If it makes enough torque, you could gear it accordingly...
     
  20. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,355

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL



    Check out Bendtsen's in Ham Lake , MN.. www.transmissionadapters.com. They do all kinds of adapters for vintage engines and he has, or had, a GMC V12 (twin sixes) on the website for eye candy. I have one of their adapters for a Buick straight eight and the materials and workmanship are excellent.

    However, for the cost and effort of adapting to the V6 Jimmy, you could put in a SBC and probably have a more satisfactory all around hauler. All the negative comments about the V6 is no accident.

    Ray
     
  21. blown240
    Joined: Aug 2, 2005
    Posts: 1,814

    blown240
    Member
    from So-cal

    Thanks for the link. Its cool that there is an adapter available, but for the cost of it, you could get a running 350.
     
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 55,935

    squirrel
    Member

    They used 3.54 ratio Dana rearends in them, other ratios were available but that's what was in the 3 of them that I've worked on/looked at. So using low gear (granny first in the SM420) is helpful to get the truck moving with that wimpy engine.

    At least that's how it seemed to me, last time I drove one. As opposed to my son's 59 chevy with the same transmission and 3.90 gears, and a 235 engine.
     
  23. Falcon Gasser
    Joined: Aug 29, 2007
    Posts: 940

    Falcon Gasser
    Member

    Not a driver for long distance but when I started a maintance job at the airport years ago we ran then in old mid to later 60's med-duty GMC plow trucks and they were work horse's. I think they were 478 and we had a old pick up with a 305 V6 and it was a pig on gas but never gave us any issues.

    Jon
     
  24. Powerband
    Joined: Nov 10, 2004
    Posts: 542

    Powerband

    Worked on School Fleet where 305 V6 was used in Suburban Carry-All 4WD School Bus fleet. Modern 305 V6 is SBC less two pistons, GMC 305 was BBC minus two...
     
  25. squirrel
    Joined: Sep 23, 2004
    Posts: 55,935

    squirrel
    Member

    a bare 305 gmc block makes a bare 454 block look small and light.
     
  26. blown240
    Joined: Aug 2, 2005
    Posts: 1,814

    blown240
    Member
    from So-cal

    Well it definatly sounds like a drivetrain I dont want. But i may end up with it if the rest of the truck is worth it. I will just have to do a 350/350 swap.
     
  27. Locomotive Breath
    Joined: Feb 1, 2007
    Posts: 708

    Locomotive Breath
    Member
    from Texas

    If you want to use it as truck then give the V-6 a try before you go with the SBC swap. A Holley 500, two barrel and a fresh set of plugs and points will wake the GMC V-6 right up. They were available with automatics from the factory and you can often find the factory adapters at a decent price. Just be sure and get all of the pieces with the adapter and make sure it is a T-400 or PG adapter. The early trucks used a Hydra-Matic and the adapters are different. The V-6 has gobs of low end torque and should pull an overdrive just fine in case you were thinking 700-R4. The mileage isn't that bad, '66 Chevy pickups with stock drivetrains aren't exactly known as gas savers either.
     
  28. I don't think so---pretty sure Jimmy V-6s were unique designs.
     
  29. blown240
    Joined: Aug 2, 2005
    Posts: 1,814

    blown240
    Member
    from So-cal

    So how bad is the gas milage if you drive it nice? Are we talking 4-6 or 10-12. I can live with 10-12, thats what my F150 got.
     
  30. Da Tinman
    Joined: Dec 29, 2005
    Posts: 4,222

    Da Tinman
    Member


    in the 4-6 range. I had a gmc pickup that had its v6 removed in favor of a 425 olds. Owner said the 425 had more power and got lots better gas mileage.
     
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