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Ok, here goes;
First, and this is important, coat all bolt threads and flanges with engine oil. It sounds like you've done this before so I hope you already know how important it is not to delete this step.
The 12mm X 163mm bolts are torqued initially to 33lb. ft.
The diagram I have shows them being tightened in an "outside-in" pattern. Working from the ends of the head and crisscrossing alternately in toward the center during this "initial" torque sequence. I find this somewhat unusual so let me know if this matches the information you have.
You then continue the process by marking the head at each bolt flange "I" mark and, using a conventional "inside/out/crisscross" pattern you turn each 12mm bolt an additional 90 degrees while also performing the first of two "step" torques to the 8 and 10mm bolts. The process is complete after repeating this step a second and final time.
The 8mm bolts are to have a final 20lb. ft.
The 10mm bolts are torqued to 29lb. ft.
DISCLAIMER:
While these specifications sound reasonable, they do not come from the HELM INC. manual so I hope they are accurate. I'm pretty sure this came from a Seloc repair manual copied to a CD. I do not and have not worked on this engine or used this procedure so I have no first hand knowledge of how effective it is. I offer this to you because you sound like you are stuck and need some direction. But, you will have to be the ultimate judge whether or not to use this or if it will meet your needs.
Good luck.
Ok, here goes;
First, and this is important, coat all bolt threads and flanges with engine oil. It sounds like you've done this before so I hope you already know how important it is not to delete this step.
The 12mm X 163mm bolts are torqued initially to 33lb. ft.
The diagram I have shows them being tightened in an "outside-in" pattern. Working from the ends of the head and crisscrossing alternately in toward the center during this "initial" torque sequence. I find this somewhat unusual so let me know if this matches the information you have.
You then continue the process by marking the head at each bolt flange "I" mark and, using a conventional "inside/out/crisscross" pattern you turn each 12mm bolt an additional 90 degrees while also performing the first of two "step" torques to the 8 and 10mm bolts. The process is complete after repeating this step a second and final time.
The 8mm bolts are to have a final 20lb. ft.
The 10mm bolts are torqued to 29lb. ft.
DISCLAIMER:
While these specifications sound reasonable, they do not come from the HELM INC. manual so I hope they are accurate. I'm pretty sure this came from a Seloc repair manual copied to a CD. I do not and have not worked on this engine or used this procedure so I have no first hand knowledge of how effective it is. I offer this to you because you sound like you are stuck and need some direction. But, you will have to be the ultimate judge whether or not to use this or if it will meet your needs.
Good luck.
Hi,
"Standard" torque is used to specify the maximum amount a given diameter bolt can be placed in tension without becoming permanently distorted or stretched beyond it's elastic properties.
Bolts actually work by acting as a spring. As a bolt approaches maximum torque it is being elongated slightly. This elongation puts the joint in a state of tension. This spring like tension keeps the fasteners from working loose because of external forces. An "over-torqued" bolt can be stretched beyond it's ability to "spring back" to it's original length and is said to have "gone plastic". In extreme cases of over tightening, the bolt diameter can be seen to change and is called "necked down". If this occurs, the bolt can no longer be relied on to hold the joint in a permanent state of tension. Eventually, sometimes very quickly, the joint will loosen and fail.
American or S.A.E. grade bolts are marked with slash marks to indicate tensile strength. 3 slashes= grade 5 and 6 slashes = grade 8....the two most common grade bolts used in the American automotive industry.
The metric or ISO grading system uses numbers on the heads of bolts to indicate "hardness". You will find 8.8, 10.9 and 12.9 stamped on the heads of metric bolts but there are a few more being used.
So, getting back to the question of "standard torque" for a bolt it comes down primarily to the bolt's diameter and grade. The higher the grade of a given diameter bolt, the higher the torque required to put it in tension.
You can Google a bolt "standard torque" chart when standard torque is called for and use the diameter and grade rating to arrive at a reliable torque setting.
On the other hand....
Specified torque is something the equipment engineers have developed for putting a given bolt into maximum tension just below failure. This is arrived at through exhaustive measurement and testing. It takes the clamping ability of a bolt right out to the edge to achieve maximum clamping and holding during thermocycling, vibration and stress.
Most bolts used in this way are considered one time use only. This is often referred to as "torque to yield" (TTY) or "torque to fail" and is used extensively in engine assembly. Primarily head to cylinder block clamping. These types of bolts should not be reused.
It is also very important to follow directions given for torquing these fasteners. The tightening sequence s and patterns are important for achieving what the engineers intended. It is also very important not to deviate from the thread lubrication recommend.. If no lube is called for, don't use any.
Bolt joints calling for thread locker (Loc-Tite) will usually specify a higher torque than standard because thread lock is not a lubricant but will actually add a friction factor to the thread interface.
That's about it.
Hope I didn't bore you.
Well, I can't account for the separation of "specified" as opposed to standard in those instructions. It could be that engineering determined that those particular bolts require a slightly different torque than "standard" as would be listed on a generic chart.
Or, it could be the manual writers simply conflated the two terms. It happens.
I didn't mean to imply that all specified torque bolts are to be considered torque to yield. My apologies if it seemed so.
Typically TTY bolts will always be called out as one use only no matter what the tightening process. And, it's not unusual for "specific torque specs" to be listed in a manual for reusable fasteners. Ad a matter of fact, my experience is that most bolts in an engine assembly have specified torque listed, the majority of which are NOT TTY. And, it is actually unusual for a mechanic to be directed to use standard torque settings. Although, most quality manuals will provide a standard torque chart for common bolts.
Hope this helps.