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Technical Small Block 350 Main Bearing Questions

Discussion in 'The Hokey Ass Message Board' started by Kyle Seal, Mar 4, 2016.

  1. Kyle Seal
    Joined: Jan 25, 2016
    Posts: 9

    Kyle Seal
    from Virginia

    I've been building a stock 350 small block and am trying to find my main bearing sizes and am hitting some issues.
    I mic'd the crank, and came up with an overall average (crank journal 1-5) of: 2.4377"
    To my understanding, the main bore size is 2.6410"
    How do I use these two numbers to arrive at a crank bearing size?
    Is this math also applicable to the piston rods?
    Thanks in advance
  2. Blakmerk
    Joined: May 15, 2002
    Posts: 302

    from St.Joe MO

    ? I'm lost ...stock crank.

    Squirrl Knows.
  3. squirrel
    Joined: Sep 23, 2004
    Posts: 44,654


    2.448" is the standard journal size, 2.438" would be .010" undersize, eh?

    similar math is applicable to the rod bearings. Standard journal size is right around 2.100", so if the crank is .010" or .020" under that then you need that undersize bearings.
  4. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 6,033


    To someone "new" with engine rebuilding, it can be confusing; PISTONS/RINGS come in OVERSIZES, rod and main BEARINGS come in UNDERSIZES. And then, you can have a.010 under mainbearing froma prior rebuild, with a little crankshaft wear this time around , and you can get the undersize bearing but then in +.001 oversize; so it's undersize AND oversize. Confused yet?
    I am Butcfh/56sedandelivery.
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  5. I measure journals in 4 places. Front and back of the journal to see if it has taper and at 90* from that to also check for possible out of round. I agree it seems to have been ground .010 under and bearings are available anywhere.

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