Subject: proper bolt torque on Farmall Cub
From: (Don)
Date: 20/07/04 15:32 GMT Daylight Time
Message-id:

I have an old 49 Farmall Cub that I am fixing for my father. I
replaced the bearings in the transmission. The old manual I found
online says the countershaft bearing retainer should be torqued to 35
ft lbs. The top clutch shaft retainer says to torque to 20 ft lbs.
Before I new this I torqued both to 20 ft lbs because of a bolt
size/torque diagram I found said this is the proper torque for a 5/16
bolt. Will I have problems? Why would there be different values?

The stronger the grade of steel a bolt is made from the higher the torque it
can be done up to. 35 ft lbs is a bit steep for any grade of 5/16" bolt though.
I've never seen anything that size in an ordinary engine needing more than high
20s ft lbs. A grade 12.9 high tensile metric 8mm would perhaps just stand that
much torque but you don't usually find that high a grade except in aftermarket
bolt sets for race engines.

30 to 35 ft lbs is about what I'd associate with a normal 9mm high tensile big
end bolt (grade 10.9) and perhaps 24 to 28 ft lbs for an 8mm one.

No point using a bolt chart if you don't know the grade of steel of the bolt
and also the strength and thread length of the parent material it's screwing
into.


--
Dave Baker - Puma Race Engines (www.pumaracing.co.uk)
Regione interior.....Scorchio
Regione exterior....Scorchio
Costa...................Scorchio
Chalfont St Peter...Cumulo bloody nimbus as per usual.