Faced with replacing two broken valve springs on an ancient 4-cylinder engine, I found springs of the correct diameter and correct wire size. The stock spring was longer and stronger, so I gambled on some homegrown metallurgy. The replacement springs were fully compressed with bolts and washers, then cooked in a gas grill on the highest flame for three hours with the cover closed, then allowed to slowly cool in the grill. The resulting springs had a reduced spring rate of 40lb/in, matching the original spring, and matching height. Poor man’s metallurgy!
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