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 - Restoration Story: Fordson Major - by Anthony West. George bought his Fordson Major from a an implement sale about 18 years ago for £200.00 (UK). There is no known history regarding its origins or what service it had done, but the following work was undertaken alone to bring it up to show standard. From the engine number, it was found that this Major was produced late 1946. It was almost complete but had various parts that would definitely need replacing.
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