engine bearings

I purchased a non running 49 M at a sale a couple weeks ago with the hopes of fixing it up. After getting it home and tearing into the engine I found that the engine had just been overhauled but the new bearings had about 50 thousandths clearance. The bearings are aftermarket and say standard on the back. My question is I'm wondering if when they ordered the bearings could they have gotten the bearings for a later model M instead of the earlier model. Do the early and late model have the same outside measurements. Just trying to figure what they did to cause this problem. Thanks Larry
 
My Dad was Service Mgr at IH Dealership. One thing he taught me. Never assume when working on crankshaft. Always mike it to determine correct size. He said he learned when working on late model car . He and owner replaced crank bearing for first time assuming them to be std. After replacement and starting with loud knocking they tore it back down, miked the crank and found it undersize from the factory when new. Of course this was back during WWII years.
 
(quoted from post at 18:11:31 08/19/13) No the crank mikes as standard. That's what I was thinking at first.

In that case, it is very likely that the bearings are for the later crank which has larger journals.
 
Like I said I had the crank miked and it checks out to be standard. As far as the bearing number they are after market and just say standard on the back
 
Think you nailed it. bearings are the same on the OD .050 difference on the ID for small diameter rod journals compared to big diameter cranks. Only difference besides the cranks is thinner or thicker bearings. Don't hold me to it but if I remember correct the mains are .060 bigger on the late crank.
49 came with a small journal, in case it was changed a crank casting number ending in DC or lower is a original small journal.
 
Parts catalog shows SN#501-278049 as early bearings.

SN#278050 & up show different part number for main and rod brgs.
 
278049 is the last engine serial number they used the smaller diameter crank with the thicker bearings. Lots of people think that's tractor serial numbers and get mixed up. Bigger diameter crank started at engine # 278050 and tractor # 291050.
 

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