'96 Sport 1.8 DOHC Clanking Valves

[rasmeidirtrider]

Hi, my Sport has clanked its valves during acceleration from stoplight. I can hear them clearly from inside the car. One of my friends recommended me to do the engine flush before an oil change which I always use 10W30 of any brands. Has anyone tried this: http://www.voltronic-germany.com/e20-engine-flush.html[/img]
Is it dangerous? Any suggestion is appreciated.
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'96 (07/95) Sidekick Sport 16V, 1.8L, 4 auto, 4x4, 4dr, A/C, ABS, in stock.