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Actual rod bore diameter in SBC

This is a discussion on Actual rod bore diameter in SBC within the Technical / Maintenance forums, part of the General Discussion category; What is the factory rod bore diameter on a 1972, 400 small block 5.565 connecting rod? All I can find ...

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    Actual rod bore diameter in SBC


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    What is the factory rod bore diameter on a 1972, 400 small block 5.565 connecting rod? All I can find anywhere is the info on the change to large journal 2.1 rods. I want to know what the size of the bore is, without the bearing, not the size of the crank throw/bore with bearings installed. My reason for this is that I have some old parts and need to determine what they are. I measured the rod bore at 2.224 – 2.225. These rods have been reconditioned, and I'm not sure how much the bores were changed, or if they were just honed a little. I plan to sell the rods, and need to be able to describe what I have. I also have some Clevite bearings, P/N CB-663 P, which I bought without yet having the crankshaft for the motor. I have found that these are correct for the 400 SBC, but the same number appears to be used for undersized bearings, as well, with customers simply specifying -.010, etc. when placing an order. There is no marking on them to identify them as standard or undersized, just the basic part number. Can the application (meaning standard or undersize) of these parts be determined from the information I have: 2.225 dia. with P/N CB-663 P? I would rather not measure the thickness of the bearings because they are still in sealed packaging, and I plan to sell them also. I am afraid of losing buyers or money by opening them, but I will if that is my last resort. I didn’t know if measuring their thickness would even help, because the bearings are designed to crush a little as things are assembled. I would have to know what this crush is in order to get my final diameter by subtracting the bearing thickness from the rod bore diameter. It is interesting to note that subtracting a standard .125 from my measured 2.225 gives me exactly 2.1. This leaves no room for bearing clearance or “crush”, but seems to indicate that the fit will be on an undersized throw. How much do those bearings crush? Can I tell what the application of my bearings is by measuring their thickness? Help!

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    Re: Actual rod bore diameter in SBC

    400 rod journals are the same as any other rods besides small-journal ones. Use the same rod bearings as a 350.

    Bearing "crush" doesn't change their thickness.

    CB-663P fits 262.5, 267, 305, 327 (LJ), 350, & 400. If yours have no "-010" or whatever, they're for std dia (not turned) journals.

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    Re: Actual rod bore diameter in SBC

    Thanks a lot, RB. I kind of thought I had ordered standard bearings. While browsing Manley's (Pro Flo valves) website, I saw that the rods they sell are 2.225 also. I'm pretty sure my rods were just given a light hone, since they still measure within .001 of that. I, too, am in SW OH. You wouldn't be interested in a 400 block and heads, would you?

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    Re: Actual rod bore diameter in SBC

    Probably not the heads, if they're REALLY "400" ones; maybe the block or other parts though.

    Yeah I'm in the Cinci / Dayton etc. sort of area. Contact me offline and we can talk about it.

    Usually when they "hone" rods, they take a smidge off the cap mating surfaces, then hone the bore. So the end result is they're the same dia (ABSOLUTELY critical) but maybe a .001" or 2 shorter (not so critical).

 

 

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