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Head gaskets

  • mikespeed35
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03 Nov 2020 05:17 #41394 by mikespeed35
Replied by mikespeed35 on topic Head gaskets
I think you misunderstood the 85% and 15% Jim, or I didn't explain it well. They were not saying to reduce the torque. They were saying that most of the torque , 85% is to overcome friction in the threads and only 15% was used to create the torque. Not sure if that is any clearer! You don't reduce the torque by 85%.
CORDiallyMike

Mike Huffman

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  • JIM.OBRIEN
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01 Nov 2020 22:36 #41383 by JIM.OBRIEN
Replied by JIM.OBRIEN on topic Head gaskets
HI Mike, I'm not sure I agree with these recommendations on our engines.

First on the studs - many times the part of the stub that goes into the block has a different fit then the upper part that takes the nut. This is because they want the nut to come off and the stud to stay in the block. This may require a little more then "hand tight" due to the fit to get the proper engagement. I agree they should not be torqued down.

On lubricating the bolts and all prior to installation and then torqueing to 15% of the recommended torque value - Most often torque values are given for dry threads. If you add a lubricant you have to reduce the torque value by a certain amount but I don't ever remember reducing it by 85%. That would mean for our Cord heads instead of torqueing to 45 ft-lbs you torque to 7 ft-lbs. There is no way that will work. I'll have to dig out my fiels and see what the recommended reduction is for lubricated threads is.

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  • mikespeed35
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01 Nov 2020 16:27 #41371 by mikespeed35
Head gaskets was created by mikespeed35
Just read a article in Auto Service Professional Mag. about head gaskets. While it is written for modern engines I thought it also could pertain to our engines as well. " A failed Head gasket is only a symptom, not the cause!" " If the head uses studs the studs should only be tightened hand tight to avoid splaying of the studs and hard head installation. Be sure to lubricate all contact areas on head bolts [ threads, washers, and underside of bolt heads.] When tightening head bolts do it in 15# increments and in a slow smooth manner, not jerking manner. Only about 15% of torque value is used to actually archive torque the remaining 85% is overcoming anticipated friction. I thought these were all interesting points.
CORDiallyMike

Mike Huffman

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