So, I go over the nebulous (.440-.470") lift numbers with the stock valve springs. What will happen?

I'm thinking of just trying to run a cam with .480" lift (268XE). The manifold has to come off, and I'm thinking the .430/.460 lift cam could just be swapped out.

Also, with a stock rocker, you never get an accurate 1.5:1 lift anyway.

Please send your thoughts...

Ben T.

 

Has nothing to do with valve springs (although the valve springs that come on Vortec heads out of the box are pure unadulterated crap, they are repacememnt truck parts intended for fleets like the phone company or similar customers), the limit is that the bottom center of the retainers smash into the top of the valve guides.

But that doesn't mean the stock Vortec head valve springs are OK with the XE268; they are utterly incapable of controlling valve motion at the levels of acceleration that the cam in question will produce. Put new ones on.

And get rid of the stock rubber rockers, if you haven't already put some 1.5 ratio steel (not stamped sheet metal though) ones on there. I highly recommend the Comp 1412, or the equivalent self-aligning ones if you still have that setup on your motor.