We can increase the seated force of the Comp Cams spring by reducing the installed height, but as we do that we are also decreasing the max. lift. Installed at a height of 1.825 the seated force would be 138 pounds. I usually target 150 pounds, so that's a little lower. That installed height will accommodate up to 0.550 inch valve lift. But the "over the nose" force at 0.550 lift is only 329 pounds due to the spring rate (only 347 pounds per inch). Both the seated force and especially the force at maximum lift are lower than the application calls for. So I can't recommend using that spring with a hydraulic roller cam application, it would be OK for a flat tappet cam with a rev limit at 6200 rpm.
I believe the Ford bolt-down (pedestal mount) rocker arms were supplied with heat treated/black oxide coated allen head cap screws (5/16 inch). With those cap screws the rocker arms should be good to 400 pounds spring force at maximum lift (over the nose). If you want a little more assurance you could substitute ARP chromoly cap screws.
The theoretical specification I penned above was based on lobes with 54° hydraulic intensity. When I get to the point of specifying a camshaft that can actually be ordered I select lobes from the Bullet Cams on-line catalog. I was able to find a matching pair of lobes with 56° hydraulic intensity (gentler ramps) providing 0.554 inch gross lift in their catalog. The lobe numbers are:
Intake = HR278/320
Exhaust = HR286/320
The spec with those lobes would be:
- Duration at 0.006 inch tappet lift = 278°/286°
- Duration at 0.050 inch tappet lift = 222°/230°
- Gross valve lift = 0.554/0.554 inch
- LSA = 114°
- Seated Overlap = 54°
- ICL = 111° ATDC (indexed +3°)
- Seated EVO = 80° BBDC
- Seated IVO = 28° BTDC
- Seated IVC = 70° ABDC
Bullet Cams make excellent cams with top workmanship and good customer service. I can provide further details (springs, timing, compression, and ordering info) if this spec interests you. If you think the spec needs adjustment I can do that too.