For the large diameter KR valve cover I suspect there are quite a variety of springs one could find nowadays suitable to the task, both single and dual-spring combinations.
However, the small diameter valve cover used on the consumer K models really backs you into a corner because the offering of small diameter springs with adequate rate and height is quite limited. Perusing spring offerings recently from a variety of vendor literature revealed a few possible candidates for the small diameter valve cover. But of course suitability may be different for each individual based on what they feel is required to control their specific valve train and cam profile. Also, I doubt any of these candidates is a direct drop-in, i.e., requires shimming, alternative collars, keepers, custom valve, etc,
The few possible candidates I ran across are the following, although I’m sure if one pursued it further there are more. The commonality between all of them are the small block Ford V-8s, both 3-valve and 4-valve varieties.
Peterson Spring, PAC-1233, ovate wire beehive design, large end OD 1.025” rate ~ 300 lb/in, max lift 0.550”. This is from their Beehive series spring offering.
Peterson Spring, PAC 1234X, round wire, beehive design, large end OD 1.021” rate ~ 240 lb/in, max lift 0.500”. This is from their RPM series spring offering and involves more processing than the PAC-1233 and is alleged to be slightly better suited to high rpm operation.
Manley, 221418, ovate wire, conical design, large end OD 1.014”, rate = 236 lb/in, max lift 0.570”. This is from their NexTek series spring offering.
Since the vendors provide data tables of spring load vs height data for each of these candidates, thought it would be interesting to plot the data for comparison, as this makes it easy to see the range of seat and open pressures possible with each spring.
- K Model valve springs.png (73.38 KiB) Viewed 15012 times