Here is a display of the three different single valve springs that Volvo used on the SOHC head.

On the left is the original size valve spring; and it's lower seat washer, and it's upper retainer. Used from 1975 until the early '80s, it is still a popular choice for those uprating the performance of their redblocks; having been proven reliable and durable to 6800rpm and a bit higher.

The part numbers for the old style spring set up:

spring: 463739-3
upper retainer: 1266797-8 [previously was 463749-2]
lower washer [seat]: 463399-6

In the middle is the spring, lower seat, and upper retainer that Volvo went with in the early '80s. It works adequately.

The part numbers:

spring: 9135130-4
upper retainer: 9135131-2
lower washer [seat]: 9135132-0

On the right is the latest version of the valve spring, introduced in the early '90s.

The part numbers:

spring: 9135130-4
upper retainer: 9135131-2
lower washer [seat]: 9135132-0

Notice that the part numbers did not change from the middle springs to the latest springs. This was unusual. Normally, when a part was superceded, the numbers were also changed. That did not occur in this instance.

Not shown is a double valve spring configuration that Volvo has had available through the years for competition use.