Flywheel bolt torque

[turckster]

From what I understood the reason for the torque turn method was because low torques can be had accurately, higher torques are inaccurate because of multiple turns or how someone pulls for the torque. If you set the initial torque low and a degree turn to achieve the final torque then each bolt torque will be more accurate and consistent. For example, E-7 and ETECH rod bolt torque had been 150 ft/lbs forever then all of the sudden it changed to something like 30 ft/lbs and 90 deg (or something like that-can''t remember exactly). Because most people were torquing rod bolts in chassis it could be a struggle to torque a bolt to 150 ft/lbs and many times it was inaccurate. But if you torqued it to 30 ft/lbs (easy peasy) then 90deg you would still get approx. 150 ft/lbs--just more accurate every time (when looking from an engineering point of view-- bolt clamp force and stretch). 

The Snap-on electronic torque wrenches(3/8 and 1/2) are a life saver. The torque turns seem to be accurate. When the 3/4" first came out someone in our shop bought one--we were replacing many heads and doing inframe overhauls. Unfortunately it was inaccurate in both ft/lbs and torque turn. After some back and forth between us, Snap-on and the engineers who designed the torque wrench, they were finally able to work out the bugs. 

[41chevy]

58 minutes ago, turckster said:

From what I understood the reason for the torque turn method was because low torques can be had accurately, higher torques are inaccurate because of multiple turns or how someone pulls for the torque. If you set the initial torque low and a degree turn to achieve the final torque then each bolt torque will be more accurate and consistent. For example, E-7 and ETECH rod bolt torque had been 150 ft/lbs forever then all of the sudden it changed to something like 30 ft/lbs and 90 deg (or something like that-can''t remember exactly). Because most people were torquing rod bolts in chassis it could be a struggle to torque a bolt to 150 ft/lbs and many times it was inaccurate. But if you torqued it to 30 ft/lbs (easy peasy) then 90deg you would still get approx. 150 ft/lbs--just more accurate every time (when looking from an engineering point of view-- bolt clamp force and stretch). 

The Snap-on electronic torque wrenches(3/8 and 1/2) are a life saver. The torque turns seem to be accurate. When the 3/4" first came out someone in our shop bought one--we were replacing many heads and doing inframe overhauls. Unfortunately it was inaccurate in both ft/lbs and torque turn. After some back and forth between us, Snap-on and the engineers who designed the torque wrench, they were finally able to work out the bugs. 

When I worked on Roll Royce C engines and Leyland Meteor V12 Diesels in 1972 in Israel, we were given a week long course on tightening fasteners. We learned that the torgue will be vary when using a deep  or shallow socket and also using an extension.

[Freightrain]

Using an extension on a torque wrench is a no no!  For the back yard kinda person, if it has to be, so be it.  But working on something much more critical it is not suppose to be used.  It adds twist and most likely a much lower torque reading.

For instance, my buddy is known for over doing stuff(does not have a light touch), so he torques the wheels on his race car.  With a real deep rim, you HAVE to use an extension.  At 100#, it is close enough.   If you have to go 200-300# I'm sure the amount of error is exponential.

[fjh]

12 hours ago, turckster said:

From what I understood the reason for the torque turn method was because low torques can be had accurately, higher torques are inaccurate because of multiple turns or how someone pulls for the torque. If you set the initial torque low and a degree turn to achieve the final torque then each bolt torque will be more accurate and consistent. For example, E-7 and ETECH rod bolt torque had been 150 ft/lbs forever then all of the sudden it changed to something like 30 ft/lbs and 90 deg (or something like that-can''t remember exactly). Because most people were torquing rod bolts in chassis it could be a struggle to torque a bolt to 150 ft/lbs and many times it was inaccurate. But if you torqued it to 30 ft/lbs (easy peasy) then 90deg you would still get approx. 150 ft/lbs--just more accurate every time (when looking from an engineering point of view-- bolt clamp force and stretch). 

The Snap-on electronic torque wrenches(3/8 and 1/2) are a life saver. The torque turns seem to be accurate. When the 3/4" first came out someone in our shop bought one--we were replacing many heads and doing inframe overhauls. Unfortunately it was inaccurate in both ft/lbs and torque turn. After some back and forth between us, Snap-on and the engineers who designed the torque wrench, they were finally able to work out the bugs. 

Agree somewhat!  However the point that  was mentioned earlier. how many eteck  e7  or e six con rods have you seen come a part due to torquing to 150 only?  However with the heads on these engines covering such a large area I can ,see the value  in the torque turn method for this ! rocker shafts and the like not so much! We had very few issues back in the day with rocker shafts coming loose or breaking bolts till the redesign of the the head to use a 3/8 size equivalent bolt from a 7/16 size, All of a sudden we have bolts breaking  coming loose pedestal shuffle ect .many of the issues we have these days in my mind is directly related to the under sizing of fasteners or the lack of presents (Not enough) of proper fasteners! another example being the new diff design Changed from three 1/2 inch bolts  on the spur shaft  to one 3/4 inch bolt that comes loose I've seen this happen more times than I'd like ! Just some  examples! 

 

Just an opinion

[41chevy]

13 hours ago, Freightrain said:

Using an extension on a torque wrench is a no no!  For the back yard kinda person, if it has to be, so be it.  But working on something much more critical it is not suppose to be used.  It adds twist and most likely a much lower torque reading.

For instance, my buddy is known for over doing stuff(does not have a light touch), so he torques the wheels on his race car.  With a real deep rim, you HAVE to use an extension.  At 100#, it is close enough.   If you have to go 200-300# I'm sure the amount of error is exponential.

Actually there is a simple formula to figure in the length and diameter of the extensions into the torque values.