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Bearing Clerances for OMC 5.0L??-gctid351052

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    Bearing Clerances for OMC 5.0L??-gctid351052

    Hello,

    Been a while since I've been on this forum since the boat project has been on hold.

    I'm in the process of rebuilding my engine and I'm trying to find the specs for the clearance on the main and connecting rod bearings. The engine is a 1987 OMC Cobra 5.0L. The guy at the machine shop told me this is essentially a Chevy 305 that has been marinenized (SP?).

    Anyway, I've got the FSM for the power train, but it doesn't go into specifics on the internal specifications. Any ideas where I can find this? I've tried a few different internet and forum searches and keep coming up blank.

    Thanks,

    Erik

    #2
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      #3
      Thanks.
      ..........

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        #4
        Erik719 wrote:


        I'm in the process of rebuilding my engine and I'm trying to find the specs for the clearance on the main and connecting rod bearings. The engine is a 1987 OMC Cobra 5.0L. The guy at the machine shop told me this is essentially a Chevy 305 that has been marinenized (SP?).
        Erik, the main and rod bearing clearances will be pretty much standard as with the automotive version.

        I assume that you are replacing pistons as well.

        Your piston skirt clearance and piston ring end clearance will depend on which pistons you choose.

        The specs listed in the previous post are likely for the standard cast aluminum pistons.

        If you have not yet purchased pistons, there is a better selection that can be made to that of the full dished rod piston.

        The cost is minimal, and the results are well worth it, IMO.

        No matter wich piston you choose, I'd suggest that you let your machinist fit the bores to the new pistons.

        He'll know exactly what clearance to give them, and he can check ring gap as well.

        Just an FYI; when setting initial cam followers, see the info on using the static 8 stop procedure prior to oil priming and intake manifold installation.

        Do this, and you lesson the likihood of going back through them dynamically.

        Again, this is well worth doing, IMO.

        Have fun and good luck!

        .
        Rick E. Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

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          #5
          Rick,

          I've already gone with the stock pistons. The machine shop checked all the clearances with the bores and marked them all so I can get them back in the correct cyclinder. I'll have to set the ring gaps my self.

          Not sure what you were talking about in regards to the cam followers. Are you talking about setting the lash on the rockers/push rods? As I understand that procedure, you put #1 cyclinder at the bottom of the exhaust stroke and tighten the the rockers just to the point where there is resistence while spining the push rod. Then repeat for the other cyclinders in firing order.

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            #6
            Erik719 wrote:
            Rick,

            Not sure what you were talking about in regards to the cam followers. Are you talking about setting the lash on the rockers/push rods? As I understand that procedure, you put #1 cyclinder at the bottom of the exhaust stroke and tighten the the rockers just to the point where there is resistence while spining the push rod. Then repeat for the other cyclinders in firing order.
            I'm not familiar with what you're talking about, unless you are confusing this with the 2 or 3 stop procedure. However, you do mention firing order.

            The 8 stop takes us right on down the firing order, beginning with #1 cylinder TDC C/S.... C/S being the critical factor here.

            I won't bore you with the reasons for this.

            As for the cam followers being "dry" (not yet primed) and intake manifold not yet being installed, let me know if you are interested in doing this.

            It is by far the easiest and more accurate way to set the plunger depth.... and we usually don't have to go back through them.

            .
            Rick E. Gresham, Oregon
            2850 Bounty Sedan Flybridge model
            Twin 280 HP 5.7's w/ Closed Cooling
            Volvo Penta DuoProp Drives
            Kohler 4 CZ Gen Set

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