Here is some data on spring pressures - that I compiled via my own tests . . . will give you some ideas on options:
Flathead Spring Pressures
Author: Dale Hays, Vintage Horsepower,
[email protected]
Date: 08/14/2019
The following was done with a hydraulic spring tester – have used it for quite a few years and it is quite accurate (until you get below about 50 PSI).
1. Isky 185G – Single Spring (new)
• 110# @ 1.900
• 100# @ 1.950
• 85# @ 2.00
2. Isky 185G- Single Spring (used)
• 180# @ 1.605
• 82# @ 2.00
• 50# @ 2.125
3. Iaky Dual Valve Springs (I don't use them on anything)
• 80# @ 1.765
• 180# @ 1.390
4. Ford 49-53 – 0BA-6513 (from Mac VanPelt)
• 60# @ 2.00
• 45# @ 2.125
5. Lincoln Zephyr – 86H-6513 (from Mac VanPelt)
• 82# @ 2.00
• 55# @ 2.125
So - if I was going to put say a .375 Potvin 3/8 cam in a street engine, I think I'd use the LZ springs from Mac and I'd install them at 2.0625 . . . should give me about 65 lbs on the seat. So there yah have it . . . . one more opinion to add to the mess! LOL