I think I have Comp 977 springs with a 1.46" OD and if I ever went to a smaller / lighter spring with a smaller OD if I get a cam with less lift, what is required? I'm thinking the 977's did require seat work but they were on the heads when I got them.

Do they make shims/cups for smaller OD springs than what the spring seat was cut for?
For say like Comp 26918 springs which have a 1.29" OD on bottom to replace the 977s

 

Yes, even if the spring pocket has been cut you can use a smaller OD spring with the correct seat/locator.

Rich

 

Your current seat were probably not machined. I believe the stock seat will accommodate 1.46s. So why are you going with smaller OD springs anyway?

 

May be going with a cam with smaller lift so I may switch to the lighter 26918 springs to give the rest of the valve train a break too.