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BIG ISSUES
With multiple rocker arm/stud failures in a short time I'd suspect that there is mechanical binding occuring somewhere in the valve train. You should be able to locate and fix it.
First, although Trick Flow indicated that you should have adequate piston to valve clearance with a certain cam, don't assume that's true unless you've checked it. A cam that should provide adequate clearance will NOT give that clearance if it is installed significantly advanced. (A few degrees of additional advance will create piston to valve interference quicker than a few extra thousandths of lift)! Did you degree-in the cam to verify proper timing events?
Sometimes the manufacturing tolerances on the crank snout keyway, timing set, and cam pin can all stack up in the same "direction" to provide significant degrees of installed error. This could cause an advanced installation even though your timing marks align properly.
Did you change your cam, valve springs, retainers, and/or other valve train parts at the same time as installing the new rockers? New interference problems can occur with changes in specs on any of these parts.
If your new cam has more lift than the old one, several things can happen. The retainer can move down so far at max lift that it strikes the valve guide. The springs can go into coil bind. If mismatched, the springs can be too weak for the weight and acceleration rates of the cam, allowing valve train seperation ("float"[img]/phpBB/images/smiles/icon_wink.gif[/img] at high speeds. Float has the same effect on valve train parts as beating them severely with a hammer. Things break.
If your valve springs are correct specification for the cam but you changed retainers, the new retainers could be providing a different installed height, allowing coil bind and/or valve guide interference.
Check your rocker arm geometry. The roller should contact the valve stem dead center with the cam positioned at 50% of maximum lift. Put some machinists dye on the valve stem tip and rotate the engine by hand a few turns. The "wear" pattern of the roller on the valve stem tip should be centered and only about .060"-.070" wide. If it isn't so, your pushrod lengths need to be changed to achieve proper geometry. The need for a custom pushrod length isn't unusual when changing heads, valves, rockers, and/or cams/lifters. If the pushrod is quite a bit too long or too short, one surface of the rocker may be touching the mounting stud at fully open or fully closed respectively.
It is likely that one or more of the above conditions exist and you have an almost "perfect zero clearance" situation. The engine turns over okay at low rpm, but the slightest valve train bounce or seperation at higher rpms causes a collision, and breaks your parts.
Turn the engine over by hand, watching everything carefully, and I bet you'll find it. Lightweight checking springs and a dial indicator will allow you to check piston to valve conditions without pulling a head. Be sure to check that clearance carefully one degree at a time for 10 degrees on both sides of TDC. Minimum piston to valve clearance doesn't usually happen right at TDC, depending on the cam's timing. Good luck!
Steve
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