14-04-18, 09:03 PM
So i'm probably about to fire the engine for the first time tomorrow following a cam chain replacement and the deepest engine work I have ever attempted. Today I checked the valve timing as I have had the cams out (all just within spec) and after a few beers this evening something hit me:
Given that the crankshaft turns 720 degrees in one full rotation of the engine, when I re-installed the cams at TDC for piston 1, how do I know it's at TDC for piston 1 and not piston 3? Then I remembered that the HT leads are divided between 1+3 and 2+4. Does this mean that 1 and 3 spark at the same time regardless of whether the piston is in compression or power stroke? If so then it only matters that the cam chain dots lined up with the markings on the engine whilst the crankshaft is at TDC as the spark plugs spark twice per 720 degree rotation.
Or I could be wrong and tomorrow it will blow up.
Given that the crankshaft turns 720 degrees in one full rotation of the engine, when I re-installed the cams at TDC for piston 1, how do I know it's at TDC for piston 1 and not piston 3? Then I remembered that the HT leads are divided between 1+3 and 2+4. Does this mean that 1 and 3 spark at the same time regardless of whether the piston is in compression or power stroke? If so then it only matters that the cam chain dots lined up with the markings on the engine whilst the crankshaft is at TDC as the spark plugs spark twice per 720 degree rotation.
Or I could be wrong and tomorrow it will blow up.