V12 t.d.c.
#2
Brinny, this is what I would do, no doubt others will have other maybe easier methods:
Remove all the plugs so the engine is easier to turn. Then put your thumb over A1 and ask someone to turn the engine by hand using the front of the crank pulley nut CLOCKWISE as you face the engine from the front looking at the windscreen. You will feel the compression against your thumb. Then turn another two revolutions and stop just before the compression starts to get strong. You are now on the compression stroke but not yet at TDC. Take a piece of stiff wire and a cork, and drill a hole in the cork to just support the wire but be just loose enough so it can slide in the hole in the cork. Jam the cork in the plug well and let the wire slide down until it touches the piston. Turn the engine slowly until the wire stops rising. When it stops, mark the position on the crank angle scale below the pulley AND on the pulley. Then SLOWLY turn the engine until the wire JUST begins to fall. Mark only the pulley again, where it is opposite your first scale mark. Then, when you turn the engine again two more revolutions, TDC is the mid point between the two pulley marks when that mid- point is opposite the scale mark.
The reason for this procedure is that at and around TDC the piston hardly moves up or down over 2 or three degrees either side, so just taking the first high point is not necessarily dead accurate.
Now you can make a clear permanent line on the pulley and adjust the scale position so the TDC on the scale is opposite your pulley mark, so now you know you can rely on the scale.
Remove all the plugs so the engine is easier to turn. Then put your thumb over A1 and ask someone to turn the engine by hand using the front of the crank pulley nut CLOCKWISE as you face the engine from the front looking at the windscreen. You will feel the compression against your thumb. Then turn another two revolutions and stop just before the compression starts to get strong. You are now on the compression stroke but not yet at TDC. Take a piece of stiff wire and a cork, and drill a hole in the cork to just support the wire but be just loose enough so it can slide in the hole in the cork. Jam the cork in the plug well and let the wire slide down until it touches the piston. Turn the engine slowly until the wire stops rising. When it stops, mark the position on the crank angle scale below the pulley AND on the pulley. Then SLOWLY turn the engine until the wire JUST begins to fall. Mark only the pulley again, where it is opposite your first scale mark. Then, when you turn the engine again two more revolutions, TDC is the mid point between the two pulley marks when that mid- point is opposite the scale mark.
The reason for this procedure is that at and around TDC the piston hardly moves up or down over 2 or three degrees either side, so just taking the first high point is not necessarily dead accurate.
Now you can make a clear permanent line on the pulley and adjust the scale position so the TDC on the scale is opposite your pulley mark, so now you know you can rely on the scale.
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#4
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