Hmmm, sounds very much like operator error.
Is this a stock engine? With stock heads and pistons? If not, then it's possible that the valves and pistons met each other, if you didn't do all the proper prep.
What lifters were you using? Are they the fast bleed down type that minimize how radical the cam "seems" at low RPM? If so, then there's a different process for setting the lash on those. They are much noisier than a stock lifter, so the old "crank 'til the clicking stops, then crank another 1/2 turn" doesn't work for those.
To bend valves, things have to get pretty out of whack. Are you sure the cam was installed straight up? If it was off a tooth of two, then valves could have been open as the piston went to top dead center. Non-stock pistons also require consideration for valve clearance.
There's just too many unkowns here. Tell us more about what you have, what you bought and how you installed it all.
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HarryH3 - '75 K5</font color=black>
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