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What is advance timing light3/11/2024 ![]() To give the burning process a head start, an ignition advance mechanism is provided within the distributor. If not, the burning process in the combustion chamber would take longer than the speeding piston would permit, resulting in an incomplete burn. TIMING ADVANCEAs engine rpm increases, it is necessary to advance the ignition timing. To verify that the harmonic balancer and the pointer are correctly aligned on a new or rebuilt engine, bring the number-one piston to TDC on the compression stroke and confirm that the indentation on the harmonic balancer and the pointer are in alignment on zero degrees. To adjust the initial timing, slightly loosen the bolt that secures the distributor to the engine, and slowly rotate the distributor body until the initial timing agrees with the appropriate figures mentioned above. Run the engine at idle, aim a timing light at the harmonic balancer, and note the initial timing of ignition to the number-one spark plug. To check initial timing, clean the TDC (top dead center) line or indentation on the harmonic balancer at the front of the engine and, if necessary, identify it with chalk or crayon to make it more visible. Typically, they recommend 10 to 12 degrees of initial timing when the duration of the camshaft is less than 220 degrees 0.050-inch of valve lift 14 to 16 degrees of initial timing with a camshaft duration of less than 240 degrees 0.050-inch and 18 to 20 degrees of initial timing when the camshaft duration is less than 260 degrees 0.050-inch of valve lift. catalog or on their Web site under the Demon Carburetor Guide. One of the best guides to determine the initial ignition timing of V-8 engines can be found in the Barry Grant Inc. ![]() Another tip with a hi performance ignition system is when purchasing replacement Caps/Rotors is to go with a set from a known “Good Brand’ which uses Brass Cap Terminals, not cheap Aluminium terminals.INITIAL TIMINGThe chief function of initial timing is to provide a clean idle and crisp throttle response. Once you have finished checking you can simply fill the hole in the Cap with silicon RTV taking care not to let any excess Silicon inside the cap.In my experience this Air Gap problem is relatively new (within the last 10-15 years) and wasn’t a common problem with most O.E.M Caps and Rotors, but appears more common with a lot of replacement parts nowīeing sourced offshore -( its really let the buyer beware… if you aware there could be problem you can simply check it by the above method. Another thing which affects this Air Gap is not only the Radial Clearance but also Ive seen quite a difference on the vertical alignment between the different brands….which also has a big influence on the Air Gap. Anything up to 3mm Air Gap is acceptable as long as the Phasing is correct. ![]() The Air Gap is easier to check by removing all the Plugs and turning engine over by hand until the Rotor Tip comes into view at which point you should be able to see ( with a good torch) both the Tip and the Cap Terminal and using a twist drill be able to measure the Air Gap between the 2. Its quite an easy operation to perform these x2 checks on both the Rotor and the Cap by simply drilling a hole in the Cap as close as possible to any one of the Hi Tension Terminals which would allow you to clearly see the Phasing and Air Gap. This much of an Air Gap can seriously effect the Spark Performance especially if your running high compression and a big cam on the street with lots of low rpm use. ![]() and a Cap with a Large Terminal P.C.D then its very likely you could end up with up to 6mm of Air Gap between your Rotor Tip and the Cap Terminals. Of these 2 components… if you unlucky enough to have a Rotor with a ‘Short Tip’ length measured between the centre of the Rotor and the end of the Tip…. There appears to be a huge variation in dimensions closely followed by Rotor/Cap Phasing… and to a lesser extent, but still important if your chasing the best possible ignition performance is to check the Air Gap between the Rotor Tip and the Cap Terminals. Forgot to mention the first thing to check is T.D.C #1 exactly matches 0 degs on Harmonic Balancer….
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