Engine What Size Main/rod Bearings?

Discussion in '1994 - 1995 Specific Tech' started by jmil918, Mar 28, 2014.


  1. jmil918

    jmil918 New Member

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    So I've been doing some reaseach mostly out of curiousity about replacing the internals in my 95 Ford 302. The problem I'm having is deciding which bearings I will need for the crank & rods.

    The crank I'm looking into has a rod journal of 2.123 & a main journal of 2.248. My block is the stock 2.249 main journal. The rods I'm looking at show a journal of 2.123.

    My question is, if the rod journal on the rod and the crank are exactly the same number isn't that too tight right off the bat? I'm unsure of how those numbers are determined (with/without bearings in). In the crank listing it shows a .125 radius, is that the additional "room" for the journals?

    If so, am I able to use the standard size rod and main bearings or will I need an under/oversized bearing? I know that in the end plastigauge will tell me if its correct or not, but I'm wondering based on these measurements which ones would need purchased.
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  2. madspeed

    madspeed Colonel Mustard Mod Dude Founding Member

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    I usually let that stuff up to ths engine builder
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  3. jmil918

    jmil918 New Member

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    I would be rebuilding it myself, in the past I've used the same block/crank/rods so it wasn't really an issue.
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  4. revhead347

    revhead347 I have face herpes.

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    You can't rebuild an engine yourself. You can change parts in it yourself, but in order for it to be rebuilt, it requires machine work, which of course requires machines only found at a machine shop. The bearings are matched to the crank. Anything that varies from stock, requires the crank to be turned. I suggest getting your stock rods resized, and not spending the money on aftermarket rods.

    Kurt
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  5. lord_cobra

    lord_cobra Member

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    He doesn't necessarily need to bring it to a machine shop. If the cylinders check within spec you can just do bearings and rings. But it sounds like you want to replace the crank for some reason. If you do this then you should bring it in to get everything checked and balanced. The only reasons to replace the crank would be if it is shot, you are building a stroker, or spinning really high rpms and racing. All of the above I would suggest bringing it in.
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  6. jmil918

    jmil918 New Member

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    I understand that I would not be doing the machine work. This is hypothetical that I am trying to learn the measurements on. If my crank has a rod journal of 2.123 and the rods themselves have a journal of 2.123 does that mean I can use the standard (stock) size bearings.
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  7. revhead347

    revhead347 I have face herpes.

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    Yes, I guess I was the one who threw the engine rebuild term in there, and that was my fault. Yes, you should be able to use factory replacment bearings. You can plastigauge them when you are done to check the clearance. Check your rod ends for roundness. The crank usually doesn't wear much unless something goes wrong. Check the diameter to make sure it's still within in spec. If anything is off, you are going to have to have machine work done anyway.

    Kurt
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