How far those weights travel due to the stops relates to how much timing is added. The mechanical advance controls the position of the rotor and, as the speed of the engine increases, a set of advance weights begin to move outward, which adds the additional timing advance. Only, the shaft is not one solid piece, it is divided to allow the position of the rotor to move to create your total timing. You are going to need to mess with ignition timing no matter what and that entails a little more than twisting the old distributor.įirst, you have a shaft that goes straight down to the camshaft, which turns the distributor to create your initial timing. So, once you bump your initial timing up to 14-16 degrees of advance, your total advance runs out to 38-40 degrees of advance, and that is why your engine is pinging. Well, guess what, you changed your heads, cam, and added headers, all of which might like different things from your ignition timing, and even if you did not, today’s fuel likes a little more timing anyway. That might not be important if you were to run a stock engine on older gas. In other words, if your engine is designed to run with 10 degrees advanced initial timing and a total timing of 34 degrees, your distributor is going to bring in 24 degrees of advance no matter what. The reason is that the mechanical advance is going to bring in x-amount of advance. If you just adjust initial engine’s ignition timing and ignore total timing, you are likely to run into issues. For the mixture to generate force at the right moment, the spark needs to happen sooner. Despite the increase of piston speed, that fuel mixture takes the same amount of time to burn. The reason the timing needs to change is due to the increased speed of the engine. Total timing, which may be something like 34 degrees of advance, is what the timing changes to when the engine is up to speed. Initial timing, or the 10 degrees we mentioned earlier, is your timing setting at idle. What is 10 degrees advance, you ask? You have two primary settings to toy with, initial timing and total timing. That is why an engine usually has an initial timing of something around 10 degrees advance. So, you want to send the spark before the piston reaches TDC to ensure that the entire mixture is ignited at just the right time to send the piston down with the force of a complete burn. The reason is that the fuel and air mixture do not burn immediately. In the real world, the spark needs to happen a little sooner. The spark plug fires once the piston reaches the top dead center (TDC), during the compression stroke for the combustion to send the piston back to the bottom of the chamber. If you are familiar with the four-stroke engine cycle, you know that ignition comes from spark plugs. You can do some severe damage to your engine if you do not have the timing in line. It helps to understand exactly what you are tinkering with before you go making changes.
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