In order to control your valves and prevent float at higher RPMs with performance cams and larger/heavier vlaves you need to upgrade to dual springs. In order to make those dual springs fit, the vlave pocket must be cut so the inner spring will fit over the guide boss.
The customer is responsible for shipping the heads both directions.
Your packing materials must be reusable or we will charge a packing fee.
Your heads must be relatively clean, no hunks of grease and road scum or we will charge a $40 cleaning fee.
This price does not include return shipping. Actual shipping amount will be charged when your case is returned.