Re: 1982 Chrysler 105HP - timing mark help
I don't know why the engineers chose 36 degrees, but it is used to set the block pointer and then find top dead center. Unless you have the special tool or a precise depth gauge, you can not find top dead center and set your block pointer on it this way. You must feel for it OR decide that the block pointer is correct. For example, if the paint on the two screws holding the block pointer in place on its slots is not broken, then you can assume that the pointer was at that position when it left the factory and the pointer is correctly at TDC. NOW, you use the block pointer lines to find 32 degrees BTDC (old Chrysler factory recommendation) OR 30 degrees BTDC (new Chrysler factory and Force setting)
The reason for the special tool is because the piston at TDC can "rock" a couple of degrees about TDC without you being able to measure or feel it. Thus, using the tool you move it a very precise decimal number (something like .286 inches---I don't remember the exact number but they tell you in the Factory and Clymers manuals) This corresponds to exactly 36 degrees. Then, the block pointer can be set precisely at 36 degrees on the flywheel mark and timing can be accurately set to the 32 or 32 degree specification.
Because the stroke on the 125 (and Chrysler 140) is longer than other four cylinder engines (2.875 inches), 36 degrees corresponds to a larger decimal number--something like .320 inch.
Also note that the newer Force three cylinder engines have a pointer line cast into the top of the manifold. Apparently they think that this is accurate enough.
