I'm looking at getting s2 cams and only want to buy one set of springs if I decide later to do s3 cams. I was trying to compare the 2 and one says 1.54"=97lbs and the other says 1.440"=97lbs so what is the difference ?

 

Seat Pressure at the Installed height

Camshafts come with a recommended valve spring height for the intended application.

Lucky for us most of our popular cam/spring selections work together but WARNING Not all combos work, again Dependent on your use of the car. The two Springs you posted the spec on are the GSC 5041 and the Kiggly High Pressure Beehives. Both have sufficient pressure for 10k+ RPM limits and 40+ PSI boost limits.

In simpler terms they put more pressure on the valve-train. This is needed for larger cams, but could cause more wear. There is less aggressive springs are built for a more mild cam, and mild Boost/RPM limit. Some more info from Builders here:
https://www.evolutionm.net/forums/ev...s-vs-rest.html

Another thing to worry about is also the Cam compressing the valve seal, it can be a issue if running a aggressive cam. See post:
https://www.evolutionm.net/forums/ev...ain-no-go.html

So selection of the two springs would work if your planning on Cam swap to a more aggressive cam and higher power levels down the road (S2 ==> S3). Do some more reading because depending on power levels and budget you could save some money in the long run by keeping the S2's.

This is assuming your just daily driving your evo.

 

The GSC 5041's or the Kiggly's will be just fine.