APE manual cam chain tensioners are designed to replace the automatic and hydraulic tensioners on high performance engines. The automatic adjusters can back out when the throttle is closed suddenly at high rpm. This allows the cams to go momentarily out of time, and can result in bent valves and/or serious engine damage. Hydraulic tensioners have a tendency to put too much tension on the chain guide under high rpm/high oil pressure conditions, resulting in premature wear. Both problems can be eliminated with the installation of the APE manual tensioner.