MikeHynes
True Classic
Sometimes the very basics can get confusing.
Cam timing is cam timing, ignition timing is ignition timing. They are NOT the same thing.
Cam timing marks line up when the engine is at TDC for cylinder #4 (and cylinder #1) and the #4 cylinder is ready to fire. That means the valves on #4 are both closed. It also means the valves on #1 are both open (an equal amount). If you said that the cam timing marks line up when the #1 cylinder is on split overlap (both valves open an equal amount), you're correct too.
The ignition timing marks line up when the #4 OR #1 cylinders fire. Either #4 or #1 can be used for ignition timing.
Cam timing is cam timing, ignition timing is ignition timing. They are NOT the same thing.
Cam timing marks line up when the engine is at TDC for cylinder #4 (and cylinder #1) and the #4 cylinder is ready to fire. That means the valves on #4 are both closed. It also means the valves on #1 are both open (an equal amount). If you said that the cam timing marks line up when the #1 cylinder is on split overlap (both valves open an equal amount), you're correct too.
The ignition timing marks line up when the #4 OR #1 cylinders fire. Either #4 or #1 can be used for ignition timing.