Originally Posted by ap72
Well, this opinion is not only useless but in many cases wrong. The pressure the spring provides is the pressure it provides- the OD is irrelevant. A larger OD should be avoided if you can though because it does increase the mass of the spring.
Spring OD, ID, material, thickness, shape, height, coil count, etc. all go into making the spring's open and closed pressure. Increasing the OD is one of the last things they will do to increase the pressure though as it increases the mass which can lead to surge. People spend a LOT of money on spring material just to keep the OD down while supplying the required pressures.
Show me a valve spring that has 350 lb.open pressure and can be fitted at 1.750" and is 1.250" OD. You cannot can you. That blows you theory into the weeds.
IMO.........The wire diameter must be increased to increase the spring rate and must fit in a certain installed height AND diameter. If the wire diameter will not allow the spring to be fitted in a prescribed OD and height, the OD and height must be increased.
I added "IMO" just to make this self proclaimed forum cop happy.That seems to be a weed in his ***.