looking for any information on a 1970's silverado

Discussion in 'The Coffee Shop ~ Chit Chat' started by PantheraUncia, Jul 16, 2013.

  1. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    A friend of mine picked up this truck, I believe it is a 72 model silverado., it says it has a 307? that is unusual for a GM truck?





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    Last edited: Jul 16, 2013
  2. grampy

    grampy Rockstar 100 Posts

    307 is probably right, we have a 1970 C-10. It had a 307 originally, sometime in the 80's it spun a bearing and a 327 short block was installed. Should be some "experts" on here that know how long the 307 was used and in what. I'm curious, when I get some time I might do a little searching myself. KEN
  3. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    I fixed the title for you.

    I've never heard of a 307, but that's not to say they didn't exist. I do find it interesting that the sticker calls for 91 octane fuel.
  4. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Gm made two 307 engines. Chev had one in the early '70s and Olds built one in the '80's

    A friend of mine transplanted an Olds 307 into his Chev truck, but usually the trucks had the Chev 307.

    As we all know, the original Chev V8 was 265 cu in, this was bored out to create the 283 cu in engine. The 283 was rebored and stroked to create the 327.

    Then Chev got creative, they used the 327 block and the 283 crank to build the road race 302 cu in for the Camaro. The 283 block and the 327 crank gave them the 307 cu in engine.

    The 302 had lots of horsepower and the 307 had an abundance of torque.

    Both engines, and the 327, were phased out by mid '70s
  5. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    Hi Grampy, Thank's he is looking for general information about the truck and was surprised about the "307". So anything I can find out would be helpful.

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    Thank you Crawdaddy. I did not notice that, but yes the 91 octane rating for the engine is interesting.

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    Thank you RayVoy good information.
  6. RayVoy

    RayVoy Epic Member 5+ Years 5000 Posts

    Looking at the label, the spark advance is only 8 deg (not enough to require 91). The longer crank from the 327 must have raised the compression to the point where higher octane was required to prevent spark knock.
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    I dont believe the truck will be a Silverado, that particular model name didnt start until 1973 with the square body generation (1973-1987).
    Gm manufactured the 307 engine from 1968 to 1973, it was mostly found in trucks but did find its way at the factory under the hoods of sedans and stationwagons.
    This particular model engine was also used by Holden (Australia) and GM South Africa.
    Displacement: 307 cu in (5.0 L)
    Power: 115 hp
    Bore and Stroke: 3.875 in × 3.25 in (98.4 mm × 82.6 mm)
    The crankshaft is sourced from a 327 engine.
    It was originaly intended as a truck engine but use was expanded to the automobile line.
    Its common for trucks with the 307 engine to also have the "Camper Package".
    Its not especially unusual for a truck to have this engine, production numbers for small block V-8 engined trucks were about 35/65% (307/350).
    One thing to also note is most 307 equipped trucks came with manual brakes and steering while their 350 equipped cousins came with power assist brakes and power steering.
  8. PantheraUncia

    PantheraUncia Epic Member 5+ Years 1000 Posts

    Thank you Tbplus10, all great information. I will let my friend know.
  9. JTWard

    JTWard Rockstar 3 Years 500 Posts

    I can add an little something here, I have a 305 V8 in my 1990 1500 Silverado. Now a 305 is the original 1955 block with the 265 pistons, and a 350 crank and rods. The added length or stroke gave the 305 very good torque and the small pistons gave it good MPG. Also, I hate to add this, but the old 307 was one of the engines GM fitted with a "Nylon Camshaft gear". When the gear got 70K miles on it, (Or there about, it self destructed) My dad had a 1969 Chevelle hardtop with the famous 307, the engines also had big problems with camshafts. They were face hardened, and not very well done. Once you got a pile of miles on the motor the engine would develop a miss.
    Last edited: Jul 27, 2013
  10. phoebeisis

    phoebeisis Epic Member 5+ Years 1000 Posts

    I wonder if octane ratings have changed-is 91 octane in 1972 same as octane rating now?
    when i was a kid-seems like I remember some very high octane ratings on pumps-high 90's?

    Tetraethyl lead was used then(consideration for those valve seats)-compressions on some motors were high 10.5/1 and 11/1
    for big V-8s before they developed sophisticated combustion chamber designs and controls-10.5/1 was really high

    I wonder if this 91 octane is the same as current 91 octane??
    91 octane would not have been high in 1972 I think?

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