Timing marks on the 4.9L can be confusing - I've marked the correct ones in white (green fingers) on mine so they show up easily under a timing light. Those indicated by red fingers should be ignored.
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V8s are set up opposite, with numbers on the balancer, and a pointer on the engine.

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Always follow the instructions on the VECI label. Note that the correct timing setting has the large notch (10°BTDC) on the stamped steel scale.

To check if the harmonic balancer outer ring (with the timing mark) has slipped on the rubber isolator, remove the #1 spark plug (V8 RHF) and rotate the crankshaft until the pointer aligns with 0. Use a hose to blow into the spark plug hole - if it's easy, and you hear the air coming out the throttle body, rotate the crank 1 full rev back to 0, and recheck. If it's difficult (#1 compression stroke), and ALL the air comes out around the threads, drop a plastic drinking straw into the hole so it rests on the piston and rock the crankshaft gently to make sure you have the piston EXACTLY at top dead-center (straw as high as possible). Then re-check the pointer. If it's slightly off, adjust it so it's dead-on 0. If it's WAY off, replace the balancer.

Owner caption February 2013 · Photo 4892 of 5000