350 chev rebuild

Discussion in 'Gas Engines' started by mikealston2428, Mar 30, 2013.

  1. mikealston2428
    Joined: Jul 2011
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    mikealston2428 Senior Member

    Hi Guys,
    I am currently rebuilding a SB Chevy 350.
    New rings and conrod shell bearing in, I have torqued the .40 conrod bearings to 45 pnd, they are not GRP bolts so 45pnd should be correct.

    When i came to turn the engine around to torque the bolts i couldnt get at it is impossible to turn.

    Do I need to make up a tool to fit on the front pulley to get leverage or should i be able to turn it by hand ?

    With all bolts loose i can easly turn over by turning to flywheel by hand, when i torque both bolts on only one conrod i cant turn engine over at all.

    Thanks,
    Mike:?:
     
  2. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    did you lub the bearings and put oil in the cylinders?
     
  3. mikealston2428
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    mikealston2428 Senior Member

    Yes assembly lube on bearings and pots are oiled not sure whats going on ?
     
  4. DCockey
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    DCockey Senior Member

    Con rod bearings wrong size?
     
  5. troy2000
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    troy2000 Senior Member

    That seems silly at first glance, but it happened to me years ago. I bought a rebuild kit with a 'remanufactured' crankshaft, and they gave me the wrong size main bearings for what the crank had been turned down to. Like to drove me crazy for a day or two....
     
  6. mikealston2428
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    mikealston2428 Senior Member

    Bearings are .40 as they should be
     
  7. tunnels

    tunnels Previous Member

    just takes a couple of grains of dust between the conrod and the back of the bearing shell and will lock it solid !!
    Have to check the roundness of the end where the shell fits in !! use a inside micrometer and do a inside measure in a few places ,they can go out of round !! so its possible to OS outside and OS inside shells stuck that a few times !! :D:p
     
  8. powerabout
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    powerabout Senior Member

    you did do a quick and simple clearance check with plastigauge ?
    were the rods resized?
    I wouldn't change bearings without having the rods resized as when you add the new shells you will most likely have different clearances on the crank due to the rods not being round
     
  9. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    You should turn the engine after you torque each main and then each rod. That will show you if one is a problem. I always do a whole turn after each.
     
  10. 805gregg
    Joined: Apr 2010
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    805gregg Junior Member

    Plastiguage the bearings
     
  11. mikealston2428
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    mikealston2428 Senior Member

    Thanks for all the advise guys, (nothing is ever simple)
     
  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Yep, Plastigauge the bearings, somethings not right and the usual reassembly practices weren't followed (as Gonzo noted). With the rings in place, the engine will be fairly hard to turn by hand, so yes, use a socket on the crank bolt and turn in the normal rotation direction. It could be one of a number of things. Recheck all gaps and thrust faces. You can't use enough assembly lube.
     
  13. Dave T
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    Dave T Senior Member

    I've rebuilt many chevy small blocks. Did you do the diss-assembly, were all of the connecting rods and caps numbered. The first thing to check is that all the caps are on the correct connecting rods and none are turned around. If this checks out then you need to determine if the crankshaft is actually ground .040 undersize. The best way is to mike the crank. If you can't do this then you can check the clearence with plastiguage. To get an accurate check you need to have the bearings dry and tap the piston down so the top rod bearing is tight against the crank. If the plastiguage is completely flat then you probably have the wrong sized bearings then you will have to have the crank miked to determine the correct size needed. I've had reground crank kits that had the wrong size bearings. Usually the crank kit will come with plastiguage if not you can get it at most any parts suplier. Remember when rebuilding an engine keep everything absolutely clean a little grit can realy do bad things.

    Dave T :)
     
  14. mikealston2428
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    mikealston2428 Senior Member

    Thanks Dave, a lot of good detail there gives me a couple of things to check
     

  15. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    It wouldn't be the first time I've bought 10 over bearings, but received standards or 20's.
     
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