Flathead V8 Head Bolt Torque
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Tuned
Joined: Nov 2017
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From: Cicero, IN
Flathead V8 Head Bolt Torque
Getting ready to finalize the torque on the the head bolts after replacing the head gaskets on a 1953 flathead V8. The manual says 65 to 70 lb-ft. All sources I can find says 50 lb-ft dry torque for a 7/16-14 thread. The bolts have sealant on the threads so they are not dry, but not oiled either. I went to 55 lb-ft and felt like the threads were getting soft. What do you think the head bolt torque should be?
Fleet Owner
Joined: Jul 2004
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From: NM
The head bolts and the threaded holes in the block were made to a tighter thread spec at the factory, mostly to help with sealing. When in good shape they can take the 65-70 ft-lbs. But if the engine has been apart a couple of times, and especially if the holes in the block have been cleaned out with a tap, they can lose some of that tight fit. For that reason many of the "gurus" on the Ford Barn recommend only going to 55 ft-lbs, and claim success at sealing at that. Worth trying, I'd say. The effect of sealants on the torque values is hard to quantify, but it surely acts as a lubricant to some degree.
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Tuned
Joined: Nov 2017
Posts: 303
Likes: 44
From: Cicero, IN
Thanks. Yeah, in my long career as a transmission designer I learned that old cast iron threads really don't have the strength/ductility of new cast. I think I will try 5 lb-ft and see where that gets me.
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1948 - 1956 F1, F100 & Larger F-Series Trucks
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