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  • How much oil clearance for SBC main bearings?

    I was checking the clearances on my brothers 327 mains and found them to be a few tenths too big. I have generally tried to not go any bigger than .0034, staying around .0025-.003 prefered. I got .0035-.0037 on the first four mains and .004 on the last one. Should I have the main caps redone for .0003?
    Also what should I make the ring end gaps be. Plan on file fitting tomarrow. Thanks

  • #2

    Re: How much oil clearance for SBC main bearings?

    Re: How much oil clearance for SBC main bearings?

    That sounds like a lot of clearance. How are you measuring and what kind of bearings are you using? On the rings, do you have cast, hyper, or forged pistons? Are you going to use nitrous?

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    • #3

      Re: How much oil clearance for SBC main bearings?

      Re: How much oil clearance for SBC main bearings?

      Dial bore gage, and they are forged TRW with no nitrous. Bearings are clevite 77 .01-.01 under.

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      • #4

        Re: How much oil clearance for SBC main bearings?

        Re: How much oil clearance for SBC main bearings?

        I'm wondering if you trim the main caps and not the bearings, if the bearing shell might distort when you tighten it? Can you leave that 1/2 shell in the cap when you "kiss" some material off? Ring gap varies on useage and pistons. .004 per inch of bore for most applications, or around .006 per inch of bore on SOME Hyperneurotic pistons that put the top ring land higher up which sees more heat
        Should I have the main caps redone for .0003?

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        • #5

          Re: How much oil clearance for SBC main bearings?

          Re: How much oil clearance for SBC main bearings?

          No need to get the mains redone (I assume you mean align honed) because you can get .001 smaller bearings from Clevite and other manufacturers.

          I agree with you on the bearing clearance. For a car used on the street I like .0025-.0030 on the first four and .0030-.0035" on the rear main.

          If it is a strip only car then you are fine IMO. Better a little loose than a little too tight.

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          • #6

            Re: How much oil clearance for SBC main bearings?

            Re: How much oil clearance for SBC main bearings?

            Thank you for your reply. And yes, I mean align honed. But if I already am using a .010-.010 bearing wouldn't I need a .011 under to tighten them up. If so, I can't find them.

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            • #7

              Re: How much oil clearance for SBC main bearings?

              Re: How much oil clearance for SBC main bearings?

              No need to get the mains redone (I assume you mean align honed) because you can get .001 smaller bearings from Clevite and other manufacturers.
              Yep, that's what I did.
              Providing your crank is still on it's standard grind, otherwise you'll need to go another 0.010"..

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              • #8

                Re: How much oil clearance for SBC main bearings?

                Re: How much oil clearance for SBC main bearings?

                Crank is already .010 under.

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                • #9

                  Re: How much oil clearance for SBC main bearings?

                  Re: How much oil clearance for SBC main bearings?

                  I dunno. I do stuff that's mechanically challenging sometimes just for my mechanical curiousity. I'd think there'd be a way of just giving the main caps a kiss with the bearing in place and never looking back
                  Crank is already .010 under.

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                  • #10

                    Re: How much oil clearance for SBC main bearings?

                    Re: How much oil clearance for SBC main bearings?

                    I believe shaving the caps will help tighten things up a 1/2 a thou with no problems.
                    Call your machine shop and get their opinion.
                    Either that, or go 0.020" under.

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