wiper problems
 

Hey guys I have this problem with my wipers, if I hit a bump or rev my engine to much it will move my wipers(not like turn them on, just moves them like 7-10in) from the stop(base of windshield) to almost all the way up, I have tried messing with it, but can't get it figured out, also I have 74 Chevy, with 81-87 wiper linkage, its kind of annoying, and embarassing when I rev my engine to show off and my wipers move lol
Thanks for any help
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