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post #49 of (permalink) Old 08-21-2014, 03:39 PM
papajam
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1953-2018 RIP

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One must keep in mind that the 102, 104, 114, etc cam timing numbers (a format not used by Alfa, BTW) refer to degrees of crankshaft rotation, not the cams. For example, timing an intake cam to 114 means that the intake valve will be at maximum lift when the piston is at 114 degrees After Top Dead Center (ATDC); an exhaust cam at 102 means the exhaust valve will have max lift at 102 degree Before Top Dead Center (BTDC). Since the cams turn at one half crankshaft speed, one needs to calculate this into the equation.
Conveniently enough, a straight up vertical line on the cam cap is 100 degrees (or zero on your degree wheel). A mark on the cap one degree to the right of vertical equals TWO degrees of crankshaft rotation. This results in a cam timing of 102 (1 x 2 + 100 = 102). To time the intake cam to 104, your mark needs to be two degrees right of vertical (2 x 2 + 100 = 104). Same formula applies to the exhaust cam; for a 104 cam timing, the mark on the cap needs to be 2 degrees left of vertical.

Take note of where the factory marks on the caps are; 7 on intake and 1 on exhaust. This equates to 114 and 102 respectively.

Jim

Series 2 USA 1750 GTV (in Series 1 European clothing)

Last edited by papajam; 08-21-2014 at 03:41 PM.
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