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Flywheel Balance

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Cricket, Jan 5, 2005.

  1. Cricket

    Cricket 3/4 ton status

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    Ok, I'm new to the 4spd setup and swapping from TH350 to SM465. How can I tell if I have the correct flywheel. Are Chevy flywheels internally and externally balanced or just uniform for the Sm-465? What is the minimum thickness before trashing one?

    Currently I have a 350 but will be stroking it to 383 with an internally balanced Scat crank with the 350 mains, will any changes need to be made in the flywheel at that point? :confused:
     
  2. bigblock44k5

    bigblock44k5 1/2 ton status

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    As long as you are certain that the crank you are getting is internally balanced you will use a standard 350 flywheel and damper. If you were using a 400 externally balanced crank then you would use a flywheel and damper with weights on it. Flywheels are more tailored to the engine type than the tranny, you just want to make sure you get the correct clutch diameter for the flywheel and it has to be 10 spline for the input of the 465.

    Flywheels are interchangeable to cranks, so any one you get will bolt to your new crank with no mods. You dont need to worry about the minimun thickness of the flywheel because they usually go bad before they get to thin. If there are blue spots on it, it's bad. Either way, if its used, take it to get cut at a machine shop. They will also tell you if its too thin. You can get new billet flywheels on ebay for cheap, thats where I got mine. I would look for a 11" internally balanced 168 tooth flywheel. Then get a good clutch, also 11" with 10x1-1/8 splines. Coil spring type, not diaprahm. This setup will bolt right to the motor and the 465.
     
  3. Cricket

    Cricket 3/4 ton status

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    Well let's say I am looking at a used flywheel with no idea what motor it's been behind. Is there a visual difference between the internal and external types that would tell you it had been behind a 400 ext or 350 int.
     
  4. bigblock44k5

    bigblock44k5 1/2 ton status

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    Yes, on the inside of the flywheel(the face opposite where the clutch would ride)you will see a weight cast into the flywheel toward the outside near the ringgear. Its about 5" long and 1/2" wide.

    Internal:
    [​IMG]
    External:
    [​IMG]
     
  5. Cricket

    Cricket 3/4 ton status

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    Ah Ha!

    Many thanks bigblock, That is exactly what I needed. The back of mine has 3 small tabs but not the large weight. My IQ just went up .00001.

    Thanks for taking the time to help, I appreciate it!
     
  6. bigblock44k5

    bigblock44k5 1/2 ton status

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    NP, Glad to help.
     
  7. CaveBlazin

    CaveBlazin 1/2 ton status Premium Member

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    I wanted to add something to the great knowledge already being passed to you. I just recently stroked my engine and I had my block internally and externally balanced for that much more acuracy!! I bought the 400 flywheel brand new with a Lifetime warranty for 100 bucks let me know if you are interested in such a setup and i'll give you the companies info. Good luck with you setup.
     
  8. Cricket

    Cricket 3/4 ton status

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    Hey Caveblazin.

    Can you balance both internally and externally? That's not something I'm familiar with. I'd be more than interested to hear about it.
     
  9. bigblock44k5

    bigblock44k5 1/2 ton status

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    He had to externally balance his motor because it was a 400 crank. Then he probably had the reciprocating assembly balanced at a machine shop. This is a common practice for and engine rebuild, and a good idea for you too. They spin bablance everything to include the crank,balancer,flywheel, rods, and pistons. After doing this they drill or add weight to the crankshaft counterweights.

    All externally balanced motors are techinically internal and external balanced. They still have counterweights on the crank. They just need extra weight on the flywheel and balancer to due the longer stroke. ie.-400 and 454 are the longer stroke engines of the small and big block family but the block will not allow larger counterweights. Sometimes the crankshaft counterweights are filled with lead or another dense metal so external balancing is not req'd.
     

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