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piston downbore of Chevy 350? help please

Discussion in 'The Garage' started by sled_dog, Aug 19, 2003.

  1. sled_dog

    sled_dog 1 ton status

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    Anyone know what the Downbore of a 350 running 6" rods with flat top w/valve relief Speed Pro pistons would be?
     
  2. Beast388

    Beast388 1/2 ton status

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    uh???.....downbore????? /forums/images/graemlins/confused.gif

    What do you mean? /forums/images/graemlins/1zhelp.gif

    Are you looking for the compression height?
     
  3. sled_dog

    sled_dog 1 ton status

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    yep. trying to figure compression. Designing a circle track motor for my dad and wondering what compression I would be running with that setup and Vortec heads. Need to look around for heads, don't really want to get Vortecs cause I would have to get a new single plane victor 2 bbl intake then.
     
  4. sled_dog

    sled_dog 1 ton status

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    piston downbore as I understand it is how far the top of the piston is from the top of the deck at TDC
     
  5. Donovan

    Donovan 1/2 ton status

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    If you are running a Felpro Gasket that is .039" thick I will put the piston out of the hole about .005-.010" . You don't want the piston any further down in the bore than .006".
     
  6. Beast388

    Beast388 1/2 ton status

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    Oh....you are refering to deck height. It is where the term "decking the block" comes from.

    That all depends on alot of factors like block, crank, rod, and piston machining tolerances. Ideally you want a zero deck. But in actual operating conditions you need to have some clearance.

    When I mocked up my current engine, no two cylinders had the same deck height. It varied between 0.015" and 0.025" I had the block square decked so that the pistons were 0.004" in the hole. This makes for good quench and cylinder cooling etc. /forums/images/graemlins/thumb.gif

    So in answer to your question, there is no way to know for sure unless you measure each cylinder in that engine. /forums/images/graemlins/thumb.gif
     
  7. Beast388

    Beast388 1/2 ton status

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    [ QUOTE ]
    If you are running a Felpro Gasket that is .039" thick I will put the piston out of the hole about .005-.010" . You don't want the piston any further down in the bore than .006".

    [/ QUOTE ]

    I ran the 0.041" thick Fel-Pro to give me the standard clearance of 0.045" This was ideal with the pistons and rods that I am using. /forums/images/graemlins/thumb.gif
     

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