The advantage to torque to yield bolts is that once they have been correctly tightened and yielded, they will more closely follow the expansion and contraction cycles that an engine will see. It is a given that aluminum and cast steel have different coefficients of expansion. For that reason, aluminum heads on a cast steel or cast iron engine block have always been a problem.
Going back in time, in the 1970s, I was working in a Buick dealership. We had several models that had aluminum heads. The 1964 Special had a 300cid V-8 with aluminum heads. That engine needed the head gaskets replaced about every 30k miles. They used some fancy flange bolts with special washers for head bolts. Still ate up head gaskets.
Later, in the 1980 era, I was working in a Ford dealership when we first saw the stretch bolts in Escort engines. Then around the introduction of the 1.9 engine, head gasket problems reappeared. The factory reps selected several cars with gasket failures, and sent out brand new complete engines to replace them with. They took the failed engines back to Dearborn, and analyzed the failures. That was a big step in head gasket technology.
The gist of the whole thing is that modern engine have much better head gasket life with the torque to yield bolts. The factory engineers tell us not to re-use the bolts. They are much smarter and better educated than I am, so I follow their advice. If you want to take your chances with used stretch bolts, that is your choice. However, I do disagree with recommending it to other less experienced and less knowledgeable folks. That way, when a failure occurs, it will not be because I told somebody to take a shortcut or to "cheap out" on doing it properly.
I do enjoy working on cars up to a point, but I do not want to keep doing the same job on the same car over again for a couple of reasons - time consuming would be one reason and cost would be a second.
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Today's Featured Article - Grain Threshing in the Early 40's - by Pat Browning. The setting is rural Wisconsin, halfway between East Troy and Elkhorn, on Hodunk Road, our nation was at war, and I was 6, 7 and 8 years old. George was our "threshing neighbor." He was the one with the threshing machine, a JI Case on steel wheels, and he pulled it to our farm with a JI Case standard tractor also on steel. In those days, steel wheeled implements were common. The roads were general gravel, so the lugs cutting into them wasn't a problem. George would set up the thresher, s
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