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| Traditional timing of a V4 is done at 800 or less RPM. This effectively mutes the mechanical (centrifugal advance) in the distributor. The vacuum hose is also disconnected to defeat the distributors vacuum advance.. The timing cover is marked with at +3, 0, -3, -6, and -10 degrees of advance and the balance shaft pulley is scribed with a mark at TDC. Timing is set by rotating the distributor and observing (illuminated by a strobe) the TDC mark on the pulley relative to the timing marks on the cover. A high performance engine will often be set with greater advance than is possible to "dial" in using the above method. In many cases, fully played out ignition timing will be set as high as 37 degrees. It should be noted that HiPo distributors rarely have vacuum advance and some do not even have mechanical advance (race engines). The "tool" pictured above can be used to scribe additional marks on the balance shaft pulley. It is the exact size of the pulley face and is temporarily taped to the pulley to facilitate scribing (with a small file) new marks. NB the pulley turns counter clockwise. With new marks on the pulley at 10, 20, and 30 degrees it is possible to measure any amount of advance from 0 to 39 degrees. In my HiPo engines I use early V4 distributors which have a more aggressive mechanical advance curve relative to later ones. I remove the vacuum advance. Timing is set at 3000 RPM. Total advance ranges from 35-38 degrees (21 - 24 degrees of static advance). NB running this much advance is an invitation to predetonation. Use high octane fuel. The engine in Yellow Thunder has 14:1 compression and runs at 38 degrees of advance. It demands 112-114 octane fuel (not your everyday pump gas) |