Look at a picture of a brake rotor, they cannot be installed backwards.
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do not remember what it was about the rotors and the pads exactly its been 46 years please!
Some disc brake rotors are directional, and on occasion, somebody manages to install a Right Side Rotor on the Left Side.
Re piston rings - their rotational performance may vary, and there is a chance that the gaps might line up. That line up, may also occur for a cylinder that has other physical problems, accounting for some of a noticeable (or not noticeable, yet) “weak cylinder” performance.
Engine work (and work on machinery) requires much greater attention to detail, than expected (such as, when you least expect it). And there may be (and sometimes often), many opinions about almost every little detail.
In addition, there is frustration because things can break, during the work, and so the work becomes more expensive than estimated. Customers who do not know a lot about the details, may become unhappy to say the least.
On the other hand, some customers know something (or “a lot”) that conflicts with the technical details re what is broken or not working. Some of these customers, you may be able to educate; some, no. Can be very frustrating.
Does not help, to have service management - especially among the name brand automobile/truck manufacturers’ official service zones - uttering: “Hey, they’re all like that” when you find a problem, about which, the service mgt. tries to convince you it is not a problem.
One of the best mechanics I knew, was Eddy. He was a true artist in the trade. Other mechanics who “worked” at the dealership, in order to have “buddies” during the daytime, all know, that they did not . . . have knowledge.
Eddy was around for a few years and then departed. He was a fellow to hang around and learn things, the details of very careful workmanship.
A new car had a problem: it made sounds like a pop can, under certain driving and road conditions. The car POPPED, just like a can with your thumb pressing in on the side of the structure. Had never heard the problem before.
That took a while to diagnose, because the problem lay where not expected. At the factory, the spot welding ROBOT was not aware of a sheet metal stamping error.
Therefore, the floor pan and rocker arm mating surface lips were not where the ROBOT was set up to expect, and thus, the spot welds were barely landing upon and welding the edges of the lips — instead of properly welding in the meaty area (middle portion) of the lips.
The car’s floor pan was therefore flexing more than expected and POPPING on occasion.
Statistical Quality Control that does not observe every welded body, missed this car and possibly more.
The lip seam was repaired by using number 10 SS aircraft 12-point lock-nuts and 12-point screws. But I would have scrapped the car, using it for parts, given the decision by service, to not remove everything necessary to examine every spot weld of the car.
Yet I learned a valuable lesson, that paid off when another new car (same brand name) arrived from the Chicago assembly plant (UAW, of course) with the right rear wheel well having the same spot weld failure (rain water and dirt from the road, would pour in thru the gap and fill the area beneath the right rear passenger seat, and between the floor pan and floor carpet).