These springs are a drop in solution for your performance build. Using stock retainers they are super builder friendly. Here are the specs compared to stock. Upgraded rockers are recommended

good for .400 max lift and 7500 rpm

Also never use aluminum retainers, they wear and introduce particles in your oil. They also are known to fail , its now a question of ‘‘if’’ its a question of ‘‘when’’.

Stock:

Height - pressure

1.270 - 5lbs install height

1.170 - 15 lbs

1.070 - 20 lbs

.970 - 35lbs

.870 - 45 lbs

These performance springs

1.270 - 65 lbs install height

1.170 - 80 lbs

1.070 - 100 lbs

.970 - 120 lbs

.870 - 140 lbs