340 head torque requirements

66fs said
Preload should be higher due to stronger material of the fastener. Cast Iron is good to at least grade 8. Probably a nit though and I do not know in this instance. I used to have a chart, as torque is a very tricky spec. Depends on things you can not calculate. Stretch is the most accurate.

I would agree stretch is the most accurate but is it necessary to consider in this application event though Hughes Engines want to torque rocker shaft hardware to 30 vs. SM 15 ft.lbs. If the fastener does not stretch then it does not hold effectively?