408 hyd roller, too much spring pressure?
So just one question, if you’re claiming an advantage in running Beehive springs is longer life and lower spring pressures, why are you running 170 on the seat as that’s way beyond Cranes original recommendation for that cam?
The Crane recommendation assumes 1.5 rockers with .528" lift and a much higher spring rate (438lb) with a double spring.
170lb starting pressure on the seat is going to end up around 160-165lb or so after cycling. I also worked backwards with my installed heights, starting with .050" from coil bind on .584" total lift on the intake to dampen the springs at full lift (the exhaust side is .603" so their seat pressure is slightly lower).
The 1.65 T&D rockers I use are heavier and more aggressive than typical 1.5 alloy roller rockers (but they were what I had). I also have slightly heavier 2.05" valves and pushrods. The increased lift, opening and closing rates and heavier rocker, valve and pushrods all require more spring pressure to control (on top of the heavy hydraulic roller lifter). So I removed weight where I could, namely the spring and retainer.
I also had experience with a set of Pac 1218X beehive springs that were 10lb lower on the seat and about 35lb lower at full lift (313lb rate vs 353lb), and they didn't cut it. So I knew I had to step it up slightly to control the valve train. What I ended up with was a modest increase in seat pressure and open pressure and the correct springs for the job.
If I had used a double spring, then I would have required even more pressure over the nose. So I used what worked with the minimum amount of spring pressure required.
Incidentally I picked up 30rwhp by going to a 2.05" valve and 1.65 rocker being the only changes (with minor blending to suit the bigger valves). The engine makes 440 at the wheels and is nice to drive on the street.
