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What springs do I need to put in my vortec heads to accomodate the comp cams xe274 cam with 1.6 pro magnum roller rockers? I calculated the lift to be around .519/.522. Would the LT4 valve springs(GM Part #12495494) work without machine work to the heads? Also, if I put screw in studs in the heads, I won't have to run the self-aligning rockers, right?
 

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1.) Check out the Crane Cams Kit #10309-1 for Vortec Heads. The kit will install without machining the seat.
Lift can be up to 0.550" if you use stock GM retainers and @0.525" if you use Crane's retainers. (edit :eek: ...)

2.) No, use of the GM kit requires machining the seat and guide boss.
You can get the tools from Summit, Crane or Comp.

3.) Wrong :D The 3/8" screw in studs will prevent the pull-out issues associated with the factory pressed-in studs - BUT, you will still have to use 'self-aligning' rockers or you can use the Guide-plates sold by several sources for Vortec applications (with the screw-in studs).

Hope this helps;
John
 

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Discussion Starter #3
Thanks for your help John. :D
 

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The guide boss must be machined on Vortech heads FOR HIGH LIFT CAMS or oil seal to retainer contact will happen above about .470 - .480 lift or so. THE HEADS HAVE TO BE DISASSEMBLED AND MACHINED FOR GUIDE BOSS HEIGHT AND FOR POSITIVE SEALS! Many guys have tried to short cut this and two things happen - broken valve springs and cut valve stem seals.
 

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If you are going to that extent of dismantling the heads to do it correctly, might as well do it all the way, Machine spring pockets to allow a large enuff spring that will last you a long time and not more problems . If you use guide plates then self align rockers are not needed and vice versa the other way, Use guide plates ,, use good heat treated stuff. If you use the large rollers , might consider heavier springs to handle the hi rpm stuff if not use hyda rev kit.
 
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