Need some help understanding this tightening specification

[scooter123]

Got the Service Manual for the Fiesta and was looking over the procedure for Timing Belt replacement. Get to the point where the crankshaft pulley is tightened and have not a clue as to what Ford means by stages 2,3, & 4 in section 6. I understand how and why Torque can be stepped up to the final value but what I've always seen are increasing torque values, not angles. Take a look at the attached image and explain just what the heck is intended.

 

[CarGuy]

We have a timing belt?

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[Sekred]

Tighten to 74 lb.ft. Mark the head of the bolt with a white line, use a marking pen. Put a mark on the pulley that lines up with the mark on the bolt. Turn the bolt 90 degrees. Wait 2 seconds ( for the bolt to finishing stretching I assume). Turn an additional 15 degrees.
Called Torque Turning, eliminates friction affecting the procedure (how much the bolt is stretched).

 

[scooter123]

What I have difficulty with is that 90 degree rotation AFTER the initial torque to 75 ft.lbs. Been wrenching on engines since the late 60's and most bolts would snap or strip if you tried to get an additional turn that far after setting a torque value that high. Makes me wonder if they have a Bellville Washer or something similar in the mix. If not it must be a pretty long bolt to accommodate that much stretch. Actually in hindsight I would suspect that it may be a long bolt because by using one in this type of application you help insure that it's acting a bit like spring and wont ever come loose. It also explains why Ford specifies that a NEW bolt be installed instead of re-using the old one.

BTW, with only 5400 miles on my FIST I don't need a new timing belt. However I do tend to keep my cars for a long time so I am planning ahead for when a new belt is needed. After reading the procedure I expect that when that timing belt does need replacing the dealer charge will probably be pushing 1000 dollars or more. In addition all those special tools needed to do the job won't be available for more than 10 years.

 

[felopr]

What I have difficulty with is that 90 degree rotation AFTER the initial torque to 75 ft.lbs. Been wrenching on engines since the late 60's and most bolts would snap or strip if you tried to get an additional turn that far after setting a torque value that high. Makes me wonder if they have a Bellville Washer or something similar in the mix. If not it must be a pretty long bolt to accommodate that much stretch. Actually in hindsight I would suspect that it may be a long bolt because by using one in this type of application you help insure that it's acting a bit like spring and wont ever come loose. It also explains why Ford specifies that a NEW bolt be installed instead of re-using the old one.

BTW, with only 5400 miles on my FIST I don't need a new timing belt. However I do tend to keep my cars for a long time so I am planning ahead for when a new belt is needed. After reading the procedure I expect that when that timing belt does need replacing the dealer charge will probably be pushing 1000 dollars or more. In addition all those special tools needed to do the job won't be available for more than 10 years.

I know old cars just tell you just torque it to x value and that is it, but new vehicles, is not weird to see torque to x then turn y angle. Is a more accurate way to torque something. Ford is not gonna give you a value that the bolt would snap. Just do it like is in the manual

 

[Sekred]

What I have difficulty with is that 90 degree rotation AFTER the initial torque to 75 ft.lbs. Been wrenching on engines since the late 60's and most bolts would snap or strip if you tried to get an additional turn that far after setting a torque value that high. Makes me wonder if they have a Bellville Washer or something similar in the mix. If not it must be a pretty long bolt to accommodate that much stretch. Actually in hindsight I would suspect that it may be a long bolt because by using one in this type of application you help insure that it's acting a bit like spring and wont ever come loose. It also explains why Ford specifies that a NEW bolt be installed instead of re-using the old one.

BTW, with only 5400 miles on my FIST I don't need a new timing belt. However I do tend to keep my cars for a long time so I am planning ahead for when a new belt is needed. After reading the procedure I expect that when that timing belt does need replacing the dealer charge will probably be pushing 1000 dollars or more. In addition all those special tools needed to do the job won't be available for more than 10 years.

What diameter is the pulley bolt?. I will take a guess and say it is 14mm (12.9). Torque for a 14mm (10.9) bolt is around 150 lb.ft and a 12.9 is around 175 lb.ft.
Out of interest, the strut to spindle bolts are 12mm 10.9. Torque, 60 lb.ft plus 90 degrees.