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I really don't understand what ford is doing here ! torque

Step 1 torque to 25 to 32 ft lbs.
Step 2 torque to 48 to 50 ft.lbs.
STEP 3 rotate Head bolts another 85 to 90 Degrees ? why don't they have a spec for the last amount of torque.. my 302 is a bone stocker with 2 bolt mains. 7/16 Flanged Bolts. could I get a explanation for this Degree stuff or a final Torque of X Foot Lbs.. I don't have the pan bolted on yet. someone told me to do the final as 65 but this was a 4 bolt main engine.. Thanks in advance for your Help...
 

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Yeppers!
That's a "STREACH" bolt and they design the bolts to hold a certain amount of torque and then streach in the middle... I have NO clue why they do this but it's out there in MANY MANY makes of auto's.


FE
 

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The torque technique is called torque and turn. It is used often on industrial engines, foreign engines and diesel engines.
Cleanliness is a must as is lubrication. The process is to torque it to a value that will seat the gasket and provide a point from which the proper compression can be imparted to the parts by turning the bolt a given number of turns. It provides a more consistant amount of "squish" on the head gasket because the value on a torque wrench varies with the finish and amount and type of lubricant used. The problem increases substantially with higher torque values.
If you turn each bolt the same number of degrees after contact is made you will always have the same movement of parts. You are not relying on the amount of force it takes to turn the bolt - you are relying on the number of threads per inch - the distance the bolt travels down for each degree of turning - which gives you the same dimension inspite of any difference in fit, finish or contamination on the threads, bolt shank or the head of the bolt or where it contacts the head surface.
some of the engines that I have worked with have torque specs like this:
tighten all bolts in the sequence to 25 ft lbs. Back off all bolts in sequence. Tighten all bolts to 15 ft lbs. in sequence. Tighten all bolts 270 degrees in sequence. Tighten all bolts in sequence a final 135 degrees.
The Torque to yield bolts have a torquing head that breaks off - leaving a larger head that can be used to remove the bolt but the torque specs usually tell you to tighten in steps until the head yields. You always have to use new bolts and very clean threads and mating parts with a special lubricant in place. You go in steps with them to prevent turning the bolt too fast which would make the torque head yield faster than it should. That would leave you with a head that is not torqued tight enough. I tried to find a torque and turn value for my 351W when I was building it but Ford did not see fit to have a procedure for it at that time.
Paul
 
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