Not if all you are doing is replacing the rotor and/or distributor cap. If you are trying to find the correct way to wire the spark plugs then yes it is very important.
Typically it is the one that points toward the number one cylinder. Technically it can be any of them as long as the wires are in the correct firing order. When cylinder number one is a tdc, the rotor should be pointing at the number one cylinder. Thus the number one plug wire.
differential expansion is refer to differential distance between rotor blade and fix blade.rotor expand toward generator and casing expand toward control valve.when temperature increase ,expansion in casing and rotor.so rotor mass is less than casing which rotor expand more than casing.
To check if your distributor is installed backwards on a 1972 Plymouth Cuda with a 318 engine, first ensure the rotor is pointing toward the number one cylinder when the engine is at top dead center (TDC) on the compression stroke. If the rotor points away from the number one cylinder or is misaligned, the distributor may be installed incorrectly. Additionally, verify that the distributor gear is properly engaged with the oil pump drive. If you encounter difficulty in aligning the rotor with the number one cylinder, it may indicate that the distributor is reversed.
On a distributor for a 305 Chevy engine, number 1 is typically located at the front of the engine, aligned with the driver's side cylinder head. When setting the timing or installing the distributor, you should position the rotor to point toward the number 1 spark plug wire on the cap. This corresponds to the first cylinder on the driver's side, which is the front-left cylinder when facing the engine.
To set the distributor on a 455 Pontiac, first ensure that the engine is at top dead center (TDC) on the compression stroke for the number one cylinder. Align the rotor to point toward the number one cylinder terminal on the distributor cap. Next, insert the distributor into the engine, ensuring it seats properly and the rotor aligns with the terminal. Finally, secure the distributor and adjust the timing with a timing light to the recommended specification.
Number one cylinder is located driver's side front of engine. With the # 1 piston at TDC on the compression stroke, the rotor will be pointing at #1 plug on cap.Number one cylinder is located driver's side front of engine. With the # 1 piston at TDC on the compression stroke, the rotor will be pointing at #1 plug on cap.
As on any automobile engine, the rotor turns in a 360 degree circle. When the piston for the number one cylinder is at top dead center on the compression stroke the rotor should point to the number one spark plug tower of the distributor cap.
Number 1 cylinder, which would be the first cylinder on the drivers side of the engine. You want the rotor pointing towards the 5 O'Clock position looking at the distributor from the front.
Follow wire from # 1 cylinder to cap. check position of rotor. see link
In a 350 Ram Jet engine, when the number one cylinder fires, the distributor rotor is pointed towards the terminal for the number one cylinder in the distributor cap. This position ensures that the ignition spark is sent to the correct cylinder at the right moment in the firing order, allowing for optimal engine performance. Typically, this corresponds to the first cylinder on the front driver's side of the engine.
If you will remove the #1 plug, (driver's side front of engine), then turn that cylinder to top dead center, (TDC), on the compression stroke, you can then remove the distributor cap and look at the rotor. The rotor will now be pointing to the #1 plug position. GET THE NUMBER ONE CYLINDER TOP DEAD AND THE ROTOR IN THE DISTRIBUTOR SHOULD BE PIONTING AT IT
It's called a taper. Time to replace the rotors, calipers and brake pads.