Valve Spring postmortem
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Safety Car
Joined: Feb 2003
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From: St. Joseph Mo
Valve Spring postmortem
Broke a valve spring the other day on the Corvair. 
For a replacement I just dipped into my box of used parts. 
I picked out one that looked OK as far as free length and let it go at that. Later I examined the broken spring to see if I could tell what caused the break. Turns out that after a lot of miles/cycles the damper wears flats on the inside of the spring wire. The spring broke at the center of the flat. The flat/worn area is a stress riser on the notch sensitive spring wire (AISI 1090 ?). The damper itself and another I pulled out of a second spring has ROUND grooves worn in them. I'm shure that when the spring and its damper are new all you have is a line contact between the flat damper and the round spring wire. The more I think about it
the more inclined I am to use old high mile dampers inside of new springs so you end up with more bearing surface and a lower rate of wear and less chance of a stress riser.
I doubt if I would re-use old springs even if they meet load rate and free length specs. I'd have to look a little deeper.
Something to think about before you just toss the new cam and kit (lifters, springs) into your rebuilt short block.
For a replacement I just dipped into my box of used parts. I picked out one that looked OK as far as free length and let it go at that. Later I examined the broken spring to see if I could tell what caused the break. Turns out that after a lot of miles/cycles the damper wears flats on the inside of the spring wire. The spring broke at the center of the flat. The flat/worn area is a stress riser on the notch sensitive spring wire (AISI 1090 ?). The damper itself and another I pulled out of a second spring has ROUND grooves worn in them. I'm shure that when the spring and its damper are new all you have is a line contact between the flat damper and the round spring wire. The more I think about it the more inclined I am to use old high mile dampers inside of new springs so you end up with more bearing surface and a lower rate of wear and less chance of a stress riser.I doubt if I would re-use old springs even if they meet load rate and free length specs. I'd have to look a little deeper.
Something to think about before you just toss the new cam and kit (lifters, springs) into your rebuilt short block.
