The 350 is a 180 degree engine....(Crank throws and piston positions are 180* off each other)....Because the camshaft rotates at half speed (compared to the crank),and each "stroke" is a half rotation of the crankshaft, here are the relative positions/(strokes) of the two sides (piston and crank):
Starting at LTDC; (we'll call this crank position A, cam A) (L.exhaust closes, L. intake valve opens)---.[Left piston going down from TDC on intake stroke ---R. ex valve opens) Right coming up from BDC on exhaust stroke (Crank turns 180*, camshaft turns 90*)
RTDC; (Crank position B, cam B) L.intake closes) Left going up on compression stroke---R.exhaust closes, R. intake opens) right down on intake (crank turns 180* and cam 90*)
At this point, the crank has rotated 360*, and the cam 180*
LTDC; (crank position C, cam C)
(left ignition), Left down on power stroke(Both L. valves remain closed)---R. intake closes)Right up on compression (crank 180*, cam 90*)(ALL valves closed)
RTDC; Crank position D, cam D) (L. exhaust opens )Left up on exhaust--- (right ignition), Right down on power stroke (both R.valves closed)(crank 180*, cam 90*)
You will note that the points fire at 90*apart and "rest" for 270* when viewed at the camshaft end , and that this complete 4-stroke cycle has required 720*of crank rotation and 360* at the cam....
Now, let's see what happens if we advance(or retard) the camshaft by 180*.....
Since the sequence now starts Crank position A, cam C (cam C is plus or minus 180* from the original cam A position) and continues to Crank B, cam D... then crank C, cam A ...then Crank D, cam B, you would think the engine wouldn't run, BUT, Crank A and Crank C are actually the same,( both LTDC) so if the points are timed to fire at the end of the appropriate compression strokes, it runs.....
EDIT: ...Sure, figure it out while I'm composing this long reply.......LMAO!...... :lol:
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