Valve Spring / Rocker Clearance

[khryslerkid]

I'm wondering about the recommended valve springs for my Summit 6401 (911 Comp Cams valve spring) having enough clearance with my adjustable Crane rockers.

The O.D. of these springs are 1.525 and it looks like they might be a little tight. Looking for any input on someone useing this combo and their results.

 

[lewtot184]

i think the 911 is too stout for that cam. surprised it would be recommended. your picture may show a geometry problem. those aren't 911's in the picture. i'd recommend using a checking spring to run the rocker thru a cycle and check the geometry. this can't be done with a hydraulic tappet.

 

[khryslerkid]

The springs in the pic are what was on the heads when I bought them. Probably factory size. The calipers are set @ 1.525 showing the measurement that I would be dealing with. I'm thinking the 911 would be a little stout too. (306 lbs. Open pressure)
(I have a set of solids for checking)

 

[Shorthorse]

According to Crane
The ductile iron rockers -
Maximum Spring Diameter (in): 1.565 in.

 

[lewtot184]

the 911's i have tested 130lbs at 1.900", 320lbs at 1.375", spring rate is 373lbs. those rockers will test higher than their rated ratio so you'll need to compensate for that. i wouldn't doubt that you'll need maybe a .030" shim under the rocker stands but you'll have to test that.

 

[khryslerkid]

Very usefull info. Thanks Shorthorse and Lewtot184