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GMC 305 V6, The baby of the series!!!

Discussion in 'The Hokey Ass Message Board' started by revkev6, Jan 5, 2007.

  1. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    from Canada

    Yeah. The plaid covers just came on some
    special "economy series" engines. I'd sure
    like to get my hands on some of that "plaid"
    valve cover paint, but I don't think the
    dealers stock it anymore!!! LOL :D :D :D
  2. torchmann
    Joined: Feb 26, 2009
    Posts: 787

    from Omaha, Ne


    1963 gmc 305 v6 4speed 3:08 dana 44 rear all stock
    10mpg towing or not, lightfooting or not
    truck would get a little over 100mph on the highway but the brakes were scary over 55
    Thought it was a boat anchor until the machinist up at Napa told me to use premium points...
    sure nuff... just as he said even new cheap points would float out before the engine used up it's power band. the premium ponts had a good enough spring to prevent float and the 305 pulled hard after getting it tuned correctly.
    When you points float your timing goes to hell and you lose power. it takes a certain amount of dwellto build and collapse the field in the coil with a powerfull spark at the plug. (dwell= amount of points timing both opening and closing)
    If the dwell changes, the timing changes and you might lose spark.
    point float accomplishes the same thing a rev limiter does

    Truck engines used engineering features that are conflicted in a car engine... Low compression, 2 barrel carb, and something close to a high speed cam.
    It always smelled rich even when tuned right because of the higher valve overlap in the cam.
    Low compression allowed the engine to be worked hard without ping and the increased overlap in the cam allowed the 2 barrel carb to feed the large cylinders at high speed.
    The 2 barrel carb recieves a better vacuum signal than a 4 barrel from the cam.
    In other words a 2 barrel will run more vacuume, idle, and pull better than a 4 barrel below the cam's powerband.
    It's similar in some ways to the tuning tricks nascar uses to get power with restrictor plates and smaller carbs
    the 305 v6 bulky as it was needed to be wound out before shifting not lugged through the gears like a big block or a straight six.
    I suppose the highway gears coupled with the high torque worked well. I broke an axle and dropped in a 4:11 rear and it sucked and was slow.
    I hadn't yet learned that long legged engines do better with more of a highway gear.
    put short legged gears behind a long legged engine and all your doing is revving it up and going nowhere. You just took all of your power out of acceleration and moved it to tractor pulling.

    I'd rather have a 350 smallblock anyways but that 305 v6 was a champ
    Last edited: Apr 1, 2010
  3. Rocketile
    Joined: Mar 31, 2010
    Posts: 12

    from USA

    Nice... thanks for the pics. I was going to do the 500 Holley but will look into the modified Rochester's. If you are interested I will post you on what I find out on modifying the stock gerotor oil pump too. I have several 1920s era International 2 ton trucks and am planning on using the shortened frame and cab with 1970 vintage GMC 7500 running gear. Thinking of putting a brownie backwards into the drivetrain to get some serious overdrive out of it..

  4. Locomotive Breath
    Joined: Feb 1, 2007
    Posts: 711

    Locomotive Breath
    from Texas

    By all means post the oil pump mods. I would like to see the old Internationals as well.
  5. Commish
    Joined: Jan 9, 2010
    Posts: 379

    from NW Ok

    I drove a 66 single axle wheat truck with that engine from Oklahoma almost to Canada and back twice in the summers of 68 and 69. We hauled the model 95 John Deere combines up on the back of them when moving ( minus the header), and the one I drove was anything but sluggish. It had gobs of torque and pulled good loaded. It would run the speedometer easy when running empty back to the field for another load of wheat, I think it went to 85 mph.

    The only mechanical trouble I ever had was something sucked up into the needle and seat climbing up and down the hills in the Badlands of ND. Never used a drop of oil, I don't think we ever checked the mileage.
  6. Rocketile
    Joined: Mar 31, 2010
    Posts: 12

    from USA

    Sure thing... let me dig out a camera and pull some photos together. Maybe I should start a thread... Though this project is going to be lengthy:D
  7. lawman
    Joined: Sep 19, 2006
    Posts: 2,665


    Great stories and info Guy's !!!
  8. PackardV8
    Joined: Jun 7, 2007
    Posts: 890


    Getting way, way OT here, even for the HAMB:
    It was half highway and half beach



    beach track was never banked. When the cars wallowed through the turn a couple hundred turns they pushed up some sand to the outside.


    jack vines
  9. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,903


    Add to that they are heavy and to me not the easiest engines to work on.
    The spark plugs set vertical inside the valve covers and every time you tune one up you have to make sure that you blow all of the dirt and crud out from around the plugs before taking them out or it goes right down in the engine. I serviced two of them on a regular basis when I was a student in High school auto shop for all three years of high school and they were always a pain in the butt to work on.

    And now there is a limited parts availability though any regular source.
  10. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    If you did, you had carb problems AND a lead foot!
    Back in the 80's, I had a 1965 GMC pickup. 6 lug wheels, big rear window, long and wide. Red and white paint scheme. No chrome.
    Good ol' truck. Wish I'd hung onto it longer.
    My truck had the "E" engine, the heavy duty 4-speed transmission and 3.92 gears in the rear end.
    Really happy around 40-45 mph, although I drove it faster when needed (and it responded just fine).
    It could pull a house off its foundation and I averaged around 13 mpg with skinny little 7.00-15 bias ply's.
  11. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    ...and now you know why all the big trucks use diesel engines. =)
    The 637 was the replacement for the 702, after it was discontinued in......1966?, I believe.
    It's a cool ol' V8....bitchin' Rat Rod motor. =D
    My dad worked at a GMC dealership in the mid 60's, when these engines were in production and he actually didn't have good things to say about the V8.
    Too heavy for the power it put out...something like that.
    They were mainly V6's.
    The Toro-Flow diesel was an attempt at keeping the V6 alive in the 70's, but it was problematic. Not much better than the 500 "Fuel Pincher" that they tried later on.

    Truckdoctor Andy likes this.
  12. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    There's a series of youtube videos where a guy mod's his 305 intake manifold to fit a 4-bbl carb.

    ...and the revised acceleration tests...

  13. carbking
    Joined: Dec 20, 2008
    Posts: 2,914


    What happened to the 432?

  14. I have a 702 for sale if any body needs some torque.
  15. The speedometer on your truck was very likely showing a faster speed. It was a trick mechanics made to fool customers into thinking there where getting netter fuel economy. change the speedometer gear in the Trans. Ive owned several of those V6 GMC trucks. I even owned a Toro Flow Diesel truck tractor. A GMC V6 will out pull anything even close to the same load but they all guzzled fuel. They did factory install a little one bbl carb and manifold trying to get better fuel economy. That one bbl looked like a 223 ford 6 cyl. carb
    Truckdoctor Andy likes this.
  16. In the 60,s the speed limit on many two lane roads was 65 and everyone drove 70. Who in there right mind would be content going 40-45?
  17. Ah! The Toiletflow diesel! For some reason, other than Detroit’s, GM was not good at designing diesels. Toiletflow, Olds 5.7, GM 6.2/6.5, and the POS 8.2 Fuel Pincher. Should have called it the Power Pincher. That being said, the GMC gas V6’s seemed like neat truck engines. It’s pretty interesting to see those old engines doing the work they did in the medium duty field.

    Sent from my iPhone using The H.A.M.B. mobile app
  18. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    Actually, the 5.7L Olds diesel wasn't that bad of an engine.
    It mostly suffered from an uneducated public.
    In the days of the Olds diesel, the general public's conception was that ALL diesel engine were torque monsters and putting one in your pickup allowed to reverse the rotation of the Earth any time you wanted.
    Unfortunately, that's just not true. Gas, diesel or LPG, if you don't have the weight of the moving parts on your side, you're not going to be able to do much....says the former owner of a first gen VW Rabbit diesel. ;)
    So when your dad bought that brand new Chevy 1/2 ton with an Olds diesel and it didn't move the first mountain he hitched it up to, he figured the thing must be defective and traded it in for the same with a 350/350 setup, because we all knew that worked.
    Truth of the matter is, rated power for the 5.7L Olds diesel was about the same as the 2-bbl truck version of the 250 inline six of the time.
    There was a 4.3L V6 version of that engine that was used in the Cutlass Ciera and it was quite popular and well liked.
    Interesting how much perception changes when you remove two cylinder and change the application.
  19. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    When you've got 1500 lbs. or more stacked in the bed at a height double that of the cab and all you've got to stop with are 4 unassisted drums, 45 is just fine.
    A lot of trucks were rated to cruise at 45 mph due to the load potential.
    It was a safety thing.
    Especially in those days (and back even farther) highway road signs often showed the speed limit for the general public and the slower road speed for those driving loaded trucks.
    You don't see it much anymore because the factory's think they've found Nirvana with the on-board computer, so you can be as stupid as you want. The computer will stop you from killing yourself.
    Last edited: Apr 28, 2020
  20. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    Same thing that happened to the 379. They stopped making them in the 70's. ;)
  21. 6narow
    Joined: Jun 1, 2008
    Posts: 517


  22. finn
    Joined: Jan 25, 2006
    Posts: 719


    Considering the brakes of the period, 45 was plenty fast in any loaded trucks.

    Also, remember that trucks weren’t for soccer moms or cruising the mall back before the late seventies. Pickups were for farmers, plumbers , and carpenters.

    I can recall only two people in my little neighborhood that daily drove a pickup for anything but work back in the 61-64 time period . One guy had a 57 F100 short bed styleside with a 272, and the other a 62 unibody with a 223 six.

    All the others were strictly work trucks.
    6narow likes this.
  23. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    Thank you finn. I was starting to feel like the 2000 year old man.
  24. This thread brings back fond memories for me as a child. My Father was a truck mechanic at a GMC dealership in Cleveland, Ohio from '59 till the late 80's. I was born in '62, so from the time I was born I was in, on & under these trucks

    In 68 Dad bought a new 3/4 ton long bed pickup with the 305 V-6, granny gear 4 speed & a 4.10 gear. That thing would pull a house down, but wasn't much in the way of top end! LOL It was going to be my first vehicle until a woman ran a red light in a late 60's full size Ford just months before I got my license. We hit her in the pass side & basically broke that Ford almost in half. Unfortunately the front of our truck was toast & both frame rails were pushed way over...It was totaled.

    God Bless
    6narow likes this.
  25. southcross2631
    Joined: Jan 20, 2013
    Posts: 4,110


    My dad was a mechanic for the county road commission where I grew up in the U.P. of Michigan.
    they had a fleet of GMC V-6's for a while. In the winter time those dump trucks with a snow plow would make 3 1/2 to 4 mpg plowing at the desired speed of 28 mph which gave the best efficiency for the design of the plow.
    They were out there day after and night after night. Drinking gas and pushing snow. My dad really liked them because they were pretty much trouble free.
    They replaced them with the Big fords with their industrial gas engines and he said they were turds. Hard on parts and always in the shop for something.
    6narow likes this.
  26. Terry Woods
    Joined: Apr 28, 2020
    Posts: 6

    Terry Woods

    My Dad ordered and bought a new 1964 GMC half ton pickup with a 305 V6 and 4 speed granny transmission, for his farm. He was in Colorado hunting in the fall when it arrived at the dealer. I convinced the dealer to let me take delivery of it. (I was only a sophomore in high school.) The same day, I picked up two of my buddies and we when joy riding around town. Floored from a stop in 1st gear, it would burn rubber with both rear tires (positraction) until shifted into 2nd. After the shift into 2nd, it would burn a truck's length of rubber (probably 15-16 feet) before getting traction. Shifting into 3rd, it would get a tire churp (probably a foot or two). After doing this for a while, we tried it one too many times. At a stop sign, after flooring it in 1st, we hear a clang-clang-clang. We got out and looked and the rear driveshaft universal joint had broken and the driveshaft was touching the ground. We called the dealer, who sent a tow truck and took it back to the shop. I don't remember how I explained it to the dealer or my Dad, but I didn't get in trouble for it.
    Blues4U and 6narow like this.
  27. s55mercury66
    Joined: Jul 6, 2009
    Posts: 3,980

    from SW Wyoming

    I drug a '66 Suburban out of a field here a couple years ago. Mice had chewed through the primary coil wires, and all of the secondaries too. After replacing them, I poured a little gas down the carb and it started right up. I rigged up a small tank to the fuel pump, and around the yard we went. Pretty fun to get it rolling after decades of sitting, the tags on it were from 1988. I sold it to a guy in town, he went through the brakes and patched up the exhaust and drives it fairly regularly in town, the sm420/4.10 combo keeps it pretty local. He is the 4th owner, the 1st owner lives a half block away from him, and the 2nd owner, who I got it from, lives a couple doors down from him. Neither of the previous owners would believe it was the same vehicle, until he showed them copies of the paperwork. That 305 didn't tick, miss or smoke after all those years out to pasture, pretty amazing. With some 3.08's, it might make a decent highway ride, maybe we'll find out some day.
    6narow likes this.
  28. Most here daily drove their trucks. Many didn't have a car. they placed a passenger car seat in the bed and the children rode back there. Some built a plywood camper. Many had a Bill Brown stock rack. made from Post Oak lumber. the tail gate let down and had a smaller lift out gate in the center of the tail gate. The Toro Flow I owned I bought it for scrap price. the engine wouldn't run. when you poured water in it the water went straight into the oil pan. Had a new rebuilt .020 over short block. I pulled the engine and tore it down. It had the wrong head gaskets. It had 478 gas burner head gaskets. Put it back together with the correct gaskets. and the injector pump was out of time. I was stumped. Everyone I asked told me it was junk cant be fixed. Went by the Vo Tech School and asked the Diesel Mechanic Shop Teacher. He laughed called it a white elephant. He didn't know how to time the pump. However he had a Book from GMC telling everything about the Toro Flow diesel . NOS book still in the Plastic Wrap. Loaned me that book. So I timed it and it still would not run. Worked on it several days. Tried everything. We even pulled it with our 66 F600. I was in bed asleep and woke up and had been dreaming about it. I knew what I was doing wrong. 2 AM im out with a drop light timing that pump. My wife came out and brought me a cup of coffee. Debbie was setting in the drivers seat. I told her turn the key on and push the start button. She quipped It aint gonna start you done pulled it more miles than you will ever drive it. And when she hit that button it fired right up and ran perfect. That diesel turned 3200 RPM. Working 5 speed with a two speed rear. It was fun to drive. We used it all summer. Debbie drove it more than me. Installed a pintle hitch in the back and a electric brake controller and a flatbed. mover those portable buildings. And We had a 62 GMC pickup. Still had the V6 emblems on the hood. However the 305 was long gone. It was a 283 backed by a double low 5 speed. It was our escourt truck. Debbie escorted the wide loads. and we tow bared the 63 on the return trip and debbied drove the diesel.Only thing I didn't like was the wedge brakes. Sold it to a guy that put a dump bed on it and pulled his backhoe. He used it until the body rusted away. So when I returned the borrowed book I drove the truck there. Really impressed that shop teacher. He said If anyone ask I can tell them I know someone who can time a Toro Flow Diesel!
  29. was the book wrong?
  30. 6narow
    Joined: Jun 1, 2008
    Posts: 517


    My dad worked for a GMC dealership too. '65-'66. Then we moved.
    Fleming Motors in Salina Kansas.
    That building is no longer a GMC dealership, but its still an engine shop. They built the motor that's in The Farmtruck.
    Bill's Auto Works likes this.

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