Valve spring comparison
BC1100 HKS Stock

The line up is (L to R)
BC1100 (NIB)
HKS Single appox 10k miles used
Stock 2G appox 140k miles Used
Kia Looked like a 4G mutant Head, ? miles Used

Used Stock 2g spring

55lbs @ 1.530
Kia used spring

58lbs @ 1.530
HKS

60LBS @ 1.530

BC1100 New

74 lbs @ 1.530

I know it is a bit unfair to check a new spring against 3 used springs.
But this is what I had on hand at the time, I do have 2 sets of used BC1100 springs, and I will test them and post what I find with them shortly.
More Valve spring Info