What is accepted tolerance for new aftermarket valve springs?

70Hardtop said
Thanks for reply, and no I am not a journalist. I see the spring rate values given but I am not sure how to test that. It would have been nice if these Comp springs WERE 5-10% over as you say, but they are all under (except one, which was way over at 347#). It would be interesting to see the values after they had been run in an engine for a few hours. But I don't have that luxury. I will contact Comp and see what they say about it. But I don't expect much interest from them.

If you know the spring rate, you can verify that by the pressure on the seat and pressure at max lift. If the spring rate is correct that's a big deal.

I should mention you should ALWAYS check spring loads with the exact retainer you are going to use. It will affect the loads. You should never check spring load without a retainer.