Head Bolt torque to angle methodology discussion - Saabnet.com Bulletin Board

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Head Bolt torque to angle methodology discussion
Posted by Don Wollum [Email] (more from Don Wollum) on Thu, 30 Nov 2017 07:46:26
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Vintage Saab dealer factory tools for 2strokes had degree plate for rotation of head bolts once basically all bolts were screwed down in pattern to say hand wrench snug "standard. Then the angle plate was set to 30 degrees and when breaker bar movement clockwise met the "0" the head bolts were torqued properly. This was before the invention of stretch head bolts, and before calibrated click type ( read accurate ) 1/2 in torque wrenches were developed. What was in use were "springer" torque wrenches that measured tork by metal near where the socket afixed was designed to twist and the needle was reacting to arm strength applied and the needle moved and the metal 20-120 pounds on the scale plate up near the handle gave 50 pounds torque when big steadily increasing pull on handle was progressively given my technician. Springers in use were hard to execute
pulling and also observing the wavering needle, and were only calibrated once after manufacture.

Click Porque wrenches I suggest are better for ensuring head bolt torque uniformity all around, and are even better than the angle method Sabb and industry thought was an improvement at the time ( early 1960"s)

regular head bolts do stretch when torqued, and that value has to be above the over time compress ability of the head gasket material itself.

say torque head bolt to 50 pounds, 20 of that will ease away with gasket in use ( heat cycles ) compressing. and 30 pounds remain for securing steel rings that seals combustion chamber gasses alone.

retorque at 600-1000 miles, setts the clock again and the gasket shrinking any more in the future about 5%, leaving the bolts to efectively apply 40-45 foot pounds of clamping pressure.

posted by 71.50.124...

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