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My guess is lifter lost control hammered the roller bearings then flat spotted roller and then took out cam lobe and then broke link bar.
just my theory again...
I looked at your Cam spec and the lobe lift was lower that then TF cam therefore reducing the load the HR lifter were seeing with the 1.6 rockers by comparison. If I recall correctly you were not too far off the 380lbs over then nose that was required. I will do the calc again and report back...
I have been told by Howard's tech person the TF/Howards/ Morel 91767 have a design open LBS limit at just over 380lbs and seat limit of 180 lbs. Lifters call for open install of between 130 and 140 lbs and on the nose of 380 not less not more. Need the correct light weight oil too.
1.6...
Here is some interesting information that may pertain to your failure:
and
Lifters, Lash and Preload. What you don’t know won’t hurt you, or will it? - Gwatney Performance
I suspect even the Trickflow Flow Dyno results were limited by valvetrain stability rather than the trick flow heads...
I have TF top end with TF HR cam and Howards lifters 91767 on a new 440 build. I recently had multiple emails back and forth with a tech person at Howards.
He said those Howards / Morel lifter must be at 380lbs open no more no less (design limit for that lifter). That is what they can take and...