Trick Flow Heads: Conflicting Info on Mechanical Roller Spring Pressure

B3422w5 said

It’s 245/ 590 not 490.
Like I said, I ran them on a 699/672 lift comp roller at 7500 every pass for years. They tested good after 4 seasons on them.

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I'm not following what you mean by "it's 590 and not 490." 590# isn't the spring rate but what Isky lists as the max open pressure at coil bind. The 9935 spring rate is 490#, so 490 x 0.640 lift + 245# seat = 559# open, which is 90# less than what the cam grinders I talked to want for a .640 solid roller. For your cam at .699" lift, you have 588# open. I don't know what they'd recommend for a .699" solid roller, but I assume probably closer to 700#.

I appreciate that you had good results with running 588# open on a drag car with .699" lift, but it's not a fair comparison to my circle track demands. This circle track engine will see more hours on the valvetrain at 7,500 sustained rpm in one evening of hot laps, qualifying, heat, possible semi, and feature than an avid amateur drag racer's engine will see at that RPM in five years. A single 30-lap feature on a 3/8 mile is forty 1/4-mile passes with no rest on the parts. Now do that every two weekends for a season.