Torquing D15 Head Bolts

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   On Series II with 160 engine, manual says to torque them all to 80 to 85 foot pounds. All 12 of them. Except all the bolts are not the same size or spacing. 

On right side of engine, there are fewer and larger bolts. Does anyone torque those more? If so, how much. 

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modirt Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 18 Jul 2018 Location: Missouri Points: 7369	Post Options Post Reply Quote modirt Report Post Thanks(0) Quote Reply Topic: Torquing D15 Head Bolts Posted: 01 May 2023 at 4:16pm
	On Series II with 160 engine, manual says to torque them all to 80 to 85 foot pounds. All 12 of them. Except all the bolts are not the same size or spacing. On right side of engine, there are fewer and larger bolts. Does anyone torque those more? If so, how much.

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steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 81378	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 01 May 2023 at 5:10pm
	the 1/2 inch bolts can go close to 80.... the 7/16 bolts are more like 60. here is a reference... head bolts are similar to grade 8.. Edited by steve(ill) - 01 May 2023 at 5:14pm
	Like them all, but love the "B"s.

ChillyB Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 14 Apr 2023 Location: TN Points: 11	Post Options Post Reply Quote ChillyB Report Post Thanks(0) Quote Reply Posted: 03 May 2023 at 8:57pm
	What a fastener can accept before yield is not the point with head bolts. What matters is even tension. Bolt tension is a function of torque for a given thread pitch regardless of size. I don't know the thread pitch for your bolts. My first year D14 has all 7/16 bolts. My recommendation is to torque all bolts the same. The difference between tension on a 7/16-14 vs 1/2-13 probably isnt much if torqued to same value. I torqued my head to 60 ft-lb and had water in oil. Pulled to 65 ft-lb and no more problems. For what it's worth. And I used new grade 8 bolts, which could have accepted more torque but that is no reason to actually pull them that hard.

modirt Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 18 Jul 2018 Location: Missouri Points: 7369	Post Options Post Reply Quote modirt Report Post Thanks(0) Quote Reply Posted: 04 May 2023 at 7:09am
	This D15 has 7 - 7/16 bolts down left side, and 5 - 1/2 bolts down right side. The goal was to get compression of head gasket even. D15 manual says to do them all to 80 to 85 foot pounds. Somewhere I seem to recall there is another Allis engine with two sizes of head bolts and they had different torque specs. More for the larger ones. If doing them even is what works, then that is good enough for me.