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    Started to mock up engine and checked main and rod clearances. Mains are ok but rods are too tight. .0015 to .0016. I would like to have about .0002 clearance. I have been running Calico bearings so I called to get a set with extra clearance but they don't make them. I haven't found anybody that does. Any suggestions.

  • #2
    Originally posted by rioredstang View Post
    Started to mock up engine and checked main and rod clearances. Mains are ok but rods are too tight. .0015 to .0016. I would like to have about .0002 clearance. I have been running Calico bearings so I called to get a set with extra clearance but they don't make them. I haven't found anybody that does. Any suggestions.
    generally speaking turbo engines like tighter clearances, tighter clearances mean you can use lower viscosity oil, multiple benefits here, turbos generally like a thinner oil, this is because thinner oils have a lower friction coefficient (or some technical term I can't spell correctly idk) basically it means the thinner the oil an engine can run the less internal parasitic loss from friction you will experience.
    This means more power and a slightly faster spool from the turbo, 20 years ago when most of our stuff was made oils weren't as good therefore thinner oils couldn't sufficiently protect an engine, especially not one trying to turn 100,000+ miles so the factory set the base clearances on the loose side and used thicker oils slightly sacrificing power for longevity. Nowadays oil companies are making far superior products to that of 20 years ago.
    1.5 thou or.0015" sounds to me about perfect for rod bearing clearances, especially on a turbo car, Im assuming you meant 2 thousandths (.002") is the factory spec?
    What did your mains gauge out to?
    And just to be sure, the crank was re polished during the rebuild correct?
    Is this sr or ka?

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    • #3
      New BC crank and carillo rods. I think I the mains was .0016, Papers are at shop. My other motor had used crank and after polishing I had .0019 clearance on the rods which is in the ballpark. My main bearing look great after teardown but rods not so good. #3 left through the side of the block. #4 had some signs of flaking.
      I am running a Ka24de road race motor.

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      • #4
        Originally posted by rioredstang View Post
        New BC crank and carillo rods. I think I the mains was .0016, Papers are at shop. My other motor had used crank and after polishing I had .0019 clearance on the rods which is in the ballpark. My main bearing look great after teardown but rods not so good. #3 left through the side of the block. #4 had some signs of flaking.
        I am running a Ka24de road race motor.
        Those clearances should be pretty spot on to run super light racing oil, if I may recommend, http://www.schaefferoil.com/supreme-...acing-oil.html
        The only way your gonna get clearances any looser is to have the crank ground and, or re polished but I think you will make more power and run cooler using tighter clearances and thinner better oil with less friction.

        With that being said I highly recommend you take that crank out and send it off for inspection. I've seen a few cranks bc, eagle etc with tapered journals right out of the box, actually just had it happen on a 500 ci stroker motor I put together for my boss, had to under size the crank by .010" because the journals were tapered, they grew about .0007 from side to side

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