Blew up the 454 in the C30

Discussion in 'The BS Topic' started by Da_Raabi, Jun 24, 2019.

  1. Da_Raabi

    Da_Raabi Veteran Member

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    Why, oh why did GM think it was a good idea to use phenolic as a gear material in their timing gears????

    Literally the morning after I got my AC running again (its been 6 years since I've had working AC) this happened. I fired the truck up to check to see if the AC had leaked over night, it ran like CRAP for about 2 minutes then died. I tried to restart it, and it spun over like it had ZERO compression... Uh oh...

    Yes, I have bent pushrods. I pulled them all out so all the valves *should* be closed. I'm going to do a compression and leakdown test tonight (pull all the plugs and just turn the crank) to see if the valves are toast. They probably are. FML.

    1986 Chevy C30 454 with around 153,000 on it. I'm pretty sure it's all original. So far everything I have seen in the engine looks OEM original.

    IMG-20190623-WA0001.jpg
    IMG-20190623-WA0003.jpg IMG-20190623-WA0004.jpg IMG-20190623-WA0005.jpg
     
  2. RS1979

    RS1979 Veteran Member Lifetime Gold Member

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    I can remember in the 70's GM used plastic timing gears. Worst idea GM ever had. I never understood why they did that.
     
  3. 351maverick

    351maverick Veteran Member

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    motor had 153,000 miles!

    I'd say that gear lasted pretty good!
     
  4. BLUE72CAMARO

    BLUE72CAMARO Veteran Member Lifetime Gold Member

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    The phenolic was used to make the engine quieter. A good friend of mine growing ups dad had a restored bone stock 51 chevy coupe. The straight 6 in it had a gear drive timing setup in and the one entire gear was made of phenolic. I helped him replace it in the early 2000's as it lost about a dozen teeth or so.
     
  5. Da_Raabi

    Da_Raabi Veteran Member

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    That's what I keep reminding myself. Considering this was in a one-ton truck that was once used on or around a farm (although not hard based on condition) I'd say the motor held up well.

    I'm 99% sure the bottom end is in awesome shape. I've always had good oil pressure, always had great compression, and when I opened up the valve and timing covers the insides were CLEAN. NO gunk to speak of. I'm thinking, if the valves are bent, I may pick up a set of reman heads off of RockAuto for $250 each, throw in a new timing set, push rods, etc. and go for it. I REALLY don't want to pull the 454 out of the Camaro for this...
     
  6. 1980RS

    1980RS Veteran Member

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    They did that for reasons, one was the noise and second it dampens harmonics and third they were cheap to make. Bill Jenkins used them in the 70 Pro Stock stuff he said the plastic gears dampened the harmonics coming from the crankshaft to the cam, but he changed them like every race.
     
    jeff swisher likes this.
  7. bfmgoalie

    bfmgoalie Veteran Member

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    Need a hand just let me know.
     
  8. wnmech

    wnmech Veteran Member

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    E79720A8-23BE-4454-B97C-5D7A10A5D4E3.jpeg I bet GM paid for a lot of engines under warranty back then. When I tore down my 71 Z it still had the factory coated gears but the were actually still in great shape
     
  9. Da_Raabi

    Da_Raabi Veteran Member

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    Interesting the color difference. Yours is almost a yellow color while mine was a dark dark brown. I wonder what's up with that?
     
  10. Da_Raabi

    Da_Raabi Veteran Member

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    Thanks man, will do. Right now I'm just in the damage control mode. Figure out what happened and how to move forward.
     

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