Proform 66517BLTC Satin 6-3/4" Harmonic Balancer Cover
Your ignition timing can be thrown off by any number of little things. Luckily it’s easy to adjust and reset. Your engine has 4 cycles. First it sucks in air and fuel. Secondly the air fuel mixture is literally compressed tightly in the “compression stroke.” The ignition stroke is third. Finally it's the exhaust stroke. Suck, Squish, Bang, Blow. The timing of that spark has to be on cue. A fraction off will cause a loss in power and choppy idle. A little more off and you can get some serious fireworks when you don’t want them!
Using this cover improves timing accuracy because over time the etched outer inertia ring of a typical harmonic balancer may slip in relation to the center hub of the balancer, causing the markings to provide an inaccurate indication of Top Dead Center for the #1 piston. Mounted directly through the center hub, this cover eliminates the affect of any outer inertia ring slippage.
These patented harmonic balancer covers offer improved readability, more stable Top Dead Center indication and timing accuracy, enhanced appearance for a previously ignored underhood area, and the elimination of timing tapes which are inevitably flung off. Each cover is distinctively marked with Top Dead Center and the proper timing degrees. Aluminum. U.S. Patent 5,675,078.