AFR Heads
Its really not lift capability you need to look at, it is what is the seat and open forces that are required to control that cam. Once you have that information, examine the AFR base spring for installed height and seat force. Once you measure those (or know them), you need to compute the open force, clearance to the valve seal open with your lift, and distance to coil bind. All of these parameters need to be examined to determine if the correct valve spring is being used for your application.
The advertised lift capability is just a number based on a specific setup. Any changes to the setup would then change the final lift capability of the valve spring. For example, if the 0.600" advertised lift were based on a 1.800" installed height but the seat force was 120#, and you needed 135# of seat force then shims would be required to increase the seat force. Adding shims would reduce the distance to coil bind and the total lift capability of the spring would be reduced. So you really need to know the setup and take the required measurements.
If you aren't familiar with setting up valve springs, contact AFR (Tony can help) and get their input. This isn't just AFR by the way, it would apply to any valve spring setup on any head. Most guys bolt the parts in and go. Some get lucky, some don't. Make sure you understand your setup prior to installation. These are great heads, you will be happy with them once they are on the car.
The advertised lift capability is just a number based on a specific setup. Any changes to the setup would then change the final lift capability of the valve spring. For example, if the 0.600" advertised lift were based on a 1.800" installed height but the seat force was 120#, and you needed 135# of seat force then shims would be required to increase the seat force. Adding shims would reduce the distance to coil bind and the total lift capability of the spring would be reduced. So you really need to know the setup and take the required measurements.
If you aren't familiar with setting up valve springs, contact AFR (Tony can help) and get their input. This isn't just AFR by the way, it would apply to any valve spring setup on any head. Most guys bolt the parts in and go. Some get lucky, some don't. Make sure you understand your setup prior to installation. These are great heads, you will be happy with them once they are on the car.
