Timing
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Joined: Nov 2001
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From: Vermont
Timing
In the Yaw Power timing article it mentions a 8 degree split between the leading and trailing timing works best for most 12A engines. Since stock is 0 TDC degrees and 20 degrees ATDC that seems to me like a 20 degree split. Is there a reason for the big drop in the split rate from the stock one? Or am I mising something?
8krpm is not enough
Joined: Apr 2001
Posts: 422
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From: Upstate NY
Well, when you set the Paul Yaw settings, you do so at ~4krpm so all the mechanical advance has taken effect. The stock settings are at idle. Remember, there's mechanical advance on the leading ignition, then vaccum advance on both leading and trailing, so the split may very well change from idle to 4000 where the mechanical advance stops (vac advance is mainly just retard for decel, since at wot the engine produces little to no vac.).
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the 20 degree split had something to do with emissions. what, i'm not sure.
5. Stick the tape to the pulley lining up your TDC mark exactly with the TDC mark on the pulley. Looking at the pulley from the front, with TDC on top, your tape marks should be to the right of TDC, and the factory 20 degrees after TDC mark (Trailing.) should be to the left.
line it up with the leading (TDC).
i'm not sure i understood what speckamp said. mechanical on both lead and trail. if i remember correctly there are two seperate solnoids for the leading and trailing vacuum advance. so i suppose the split could change depending on vacuum, but i never bothered to look.
5. Stick the tape to the pulley lining up your TDC mark exactly with the TDC mark on the pulley. Looking at the pulley from the front, with TDC on top, your tape marks should be to the right of TDC, and the factory 20 degrees after TDC mark (Trailing.) should be to the left.
line it up with the leading (TDC).
i'm not sure i understood what speckamp said. mechanical on both lead and trail. if i remember correctly there are two seperate solnoids for the leading and trailing vacuum advance. so i suppose the split could change depending on vacuum, but i never bothered to look.
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