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PB Connecting Rod Question

Canadian PB Kid

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When I took the pistons out of the PB engine I noticed that three of the four connecting rods had numbers stamped in them (two of # 3 and a #4) and the other had 3 punch marks in the area of where the numbers are on the other rods, which is where the cap bolt goes through. One of the number 3's had a matching cap #3 and the other three caps were blank. If it matters the pistons that came out are 30 over.


My question is, Are these numbers to indicate which cylinder the rod was intended to installed in (for balance?) or was this for assembly at the plant to match rods with caps when building the Babbitt? The only one that was in the coordinated cylinder was #4. I checked the parts book and it list one number for a connecting rod for all four cylinders and it was on an exchange program.


Any advice or input would help,


Thanking in advance,





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Normally the rods and caps are numbered so the right cap goes on the right rod.  If the rods had been mis-matched in the past many mechanics would use punch marks for their own identification.  I use punch marks on everything that I disassemble.  That way I know what I am looking for when reassembling.  If the rods are not matched then they need to be line bored.  Also they should always be checked for alignment.

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