I don't know if 45 years of experience makes a difference, but unless the bolt is a "torque-to-yield" design, stretch isn't a factor. Try this experiment: Chuck a rod bolt in a lathe, and, using a small center drill, put a seat for a ball bearing in both ends of the bolt. (ARP bolts come with these holes already drilled.) Stick a BB-sized ball bearing to each end of the bolt with a little wheel bearing grease, and measure the length with a micrometer or a dial caliper. Torque the cap on, to specification, and measure the amount the bolt stretches. (ARP specifies .014" stretch on a Chevy 3/8" rod bolt) Repeat the procedure 50 times and see how much, if any, the unloaded dimension changes. Then, tell me whether or not I should re-use rod bolts. I do this on the 600+ HP, 7,500 RPM Chevy 350 race engines I build, and generally re-use the bolts several times. Head bolts are a no-brainer, unless they're rusty or have damaged threads, re-use them!
Jerry

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