Taking up the rods

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yerffej
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Taking up the rods

Post by yerffej » Fri Oct 22, 2021 11:32 pm

I have a model T that had the engine entirely rebuilt. It now has about 4000 miles on it and it developed a slight knock on #2 cylinder. Should I just take up that cap, or all four? Thank you

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JohnH
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Re: Taking up the rods

Post by JohnH » Sat Oct 23, 2021 4:34 am

My first thoughts are why it has started to knock so soon. In the modern day, bearing adjustment should last a lot longer than that. Looking at the bearing surfaces should give a clue. If the babbit looks good, it might be worth checking the roundness of the crankshaft.
One car I know of which had its engine 'rebuilt' required frequent bearing adjustment because of an out of round crankshaft.


Norman Kling
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Re: Taking up the rods

Post by Norman Kling » Sat Oct 23, 2021 9:05 am

If it was really "rebuilt", the crankshaft would either be new or turned to round. I would suspect the knock is either a crooked rod, which could cause the rod to move fore and aft, or would cock the piston slightly. Or it could be too tight a wrist pin. If it is the actual rod bearing, then it was either not completely lapped in at the time it was rebuilt or the radius at each end of the bearing was not cut to match the curve of the crankshaft. One more thing. The babbit was not poured correctly.
Norm


Scott_Conger
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Re: Taking up the rods

Post by Scott_Conger » Sat Oct 23, 2021 10:15 am

Not every T engine rebuild is a holy resurrection out of a well-known builder's shop and some rebuilds absolutely can start to knock at this kind of mileage. Twisted rods knock from the beginning...not after 4K miles.

Jeffrey

do some searches on the MTFCA forum on taking up rods. When you finally pull the inspection plate, you will find all 4 will slide back/forth on the crank with ease. When adjusted, they should still move with persuasion, but not easily by hand...again do some research. The T-1 Ford Manual from all of the suppliers should be in your bookcase and it explains the job in detail. You're doing the right thing by taking care of this now.
Scott Conger

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