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Help with torque calculations for replacement cylinder head studs Question
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Posted by: bigwalt

07/01/2004, 00:13:47

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I am replacing the original 3/8" diameter cylinder head studs on my sailboat's aux engine with beefier 7/16" diameter studs. The studs screw into the block - the cylinder head slides over studs - and then a 3/8" x 24 UNF heavy nut is used on the end of stud to tighten down the cylinder head.  The torque spec is 35 foot lbs for the original 3/8" diameter studs.

How do I calculate the proper torque value to be used on the bigger 7/16" studs so that the end result will be to yield the same cylinder head gasket compression set as the original 3/8" @ 35 ft lbs??   The nuts being used on the new 7/16" studs are 7/16" x 20 UNF fine threads.

Thanks

 

 







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glass mediaHelp with torque calculations for replacement cylinder head studs
Re: Help with torque calculations for replacement cylinder head studs -- bigwalt Post Reply Top of thread Forum
Posted by: RandyKimball
Barney
07/01/2004, 19:42:31

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I don't want to stick my mouth where it isn't welcome, however... IF.. you are replacing the 3/8 studs with 7/16 because they have not held or have stripped I would like to suggest that you consider putting inserts in the block to better hold new / better 3/8 studs. Less work, good results, have done it years ago to many VW engines, similar situation. If there is a water jacket in the head you may find that you have gotten into one when you open the holes. At times water jackets are thinner than intended or expected in areas around torque bolts.

There are several kinds of good inserts "out there" in the aircraft fastener market.

..just trying to help...

-randy-




The worst suggestion of you lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.


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Re: Help with torque calculations for replacement cylinder head studs Agree
Re: Help with torque calculations for replacement cylinder head studs -- bigwalt Post Reply Top of thread Forum
Posted by: Cragyon
Bart
07/01/2004, 09:46:37

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Check it out:  /torque.htm






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Re: Help with torque calculations for replacement cylinder head studs
Re: Help with torque calculations for replacement cylinder head studs -- bigwalt Post Reply Top of thread Forum
Posted by: mikebull

07/01/2004, 07:41:15

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A general equation is:-  Torque(lb ft) = 0.2 x Bolt Load  (lb) x noml. bolt dia (in)/12

so you can calc original load and then get new torque.  The 0.2 is the coefficient of friction.

so the new fig becomes 40.8 ft.lbs







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