![]() ![]() However, on T-Cars, the advance weights in our distributors beginning advancing the ignition at around 300-RPM. The timing must be set when the idle speed is as low as possible, i.e., just ticking over (700-800 RPM). On T-Cars, it’s not possible to set the timing using a strobe light (dynamic timing). The amazing thing is that this sequence of events can occur at rates up to and as high as 400 times a second.īefore setting the timing to TDC, there’s one more thing. Not only is the importance of precise timing obvious, the need for having tight valves is also evident. ![]() When it reaches TDC, the gas is ignited by the spark plug and the whole process starts over again. Shortly after passing BDC, the inlet valve closes and the rising piston begins compressing the gas. The piston continues down, drawing in more fuel and air. Shortly after TDC, the exhaust valve closes, sealing the cylinder except for the inlet valve. The piston passes TDC and begins to draw in a new mix of fuel and air. Just before reaching TDC, the intake valve opens. As the piston passes BDC, it begins to rise and force the burned mixture out through the open exhaust valve. The fuel has done its job and now needs to be pushed out of the cylinder. At a point before the piston reaches Bottom Dead Center (BDC), the exhaust valve opens. With space in the cylinder expanding as the piston descends, the air begins to cool. At some point, the fuel is completely burned. Following ignition, a flame front (not an explosion) proceeds across the top of the piston igniting the fuel. Of course, we know now that as the engine speeds up, the ignition point must be advanced to allow full burning of the fuel/air mixture at the same point of maximum push on the piston. Most engines fire their plugs at or very near Top Dead Center (TDC) when the engine is idling. It may be helpful here to take a moment and review what happens after ignition, if only to reinforce the notion of how critical ignition timing is. Earlier, we covered the sequence of events leading up to ignition. My knowledge on the subject is a bit limited, but according to "MG T-Series Complete Engine Tune-Up" by Skip Burns:īy now, you should have a fair understanding of ignition timing and the need for precision. I guess my question is if I hook up my 20+ year old timing light and it reads 14 btdc with the timing marks on the crank pulley remaining steady why do the timing marks jump all over the place when I hook a new advance timing light? Richard the distributor was just rebuilt so I’m sure it is functioning correctly. Can there be some sort of interference in and around the distributor that would cause both timing lights to be ineffective? Should I just replace the cap to see if that helps? I hate just guessing any help would be appreciated. The engine has new plugs and plug wires but the same distributor cap. Both of the advance timing lights were hooked up correctly with the inductive pick up lead facing in the proper direction. Same result timing marks jumping all over. Next I bought a new actron advance timing light and tried that. Moving the adjustment dial did nothing at all. ![]() When I connected it up the timing marks on the crank pulley jumped all over the place with advance set at zero. I wanted to set the total timing so I borrowed an advance timing light. ![]() Started the engine and adjusted distributor to 14 degrees btdc using my 20+ year old craftsman timing light at which point the engine ran fine. Marked the crank pulley for 10, 20 and 30 degrees. Installed the distributor making sure that the rotor pointed to #1 spark plug terminal on distributor cap when #1 cylinder was at tdc on the compression stroke. Had my distributor rebuilt by Jeff at advanced distributors.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |