Honda was one of the first manufacturers to use selective fits.
This is where parts are divided into groups based on dimensional tolerances. For example, if a crank journal is supposed to be 2.000" +/- .001" then they might be divided into three groups - 1.999", 2.000", and 2.001".
The inside diameter of the installed bearing would have a similar tolerance and groups. For example, the bearing clearance spec may be .002". Therefore, the bearing inside diameter should be 2.002". The groups might be divided into 2.001", 2.002", and 2.003".
No machining process is perfect. The size of the crank journal, the diameter of the bearing bore, and the thickness of the bearing are all going to vary a minute amount from the specification.
By matching a part (the journal size)from one group with a part from a corresponding group (of the bearing bore) they are able to achieve that .002" with more accuracy on all their engines.
By holding everything to tighter dimensional tolerances, you achieve better quality control and fewer failures. Honda started using this in the 60's or 70's and the American companies didn't start until the 80's.
I have no doubt that an American engine these days can last as long as a Honda engine. It is the fact that they have been making reliable engines longer that makes Honda have the reputation of reliability.
This is where parts are divided into groups based on dimensional tolerances. For example, if a crank journal is supposed to be 2.000" +/- .001" then they might be divided into three groups - 1.999", 2.000", and 2.001".
The inside diameter of the installed bearing would have a similar tolerance and groups. For example, the bearing clearance spec may be .002". Therefore, the bearing inside diameter should be 2.002". The groups might be divided into 2.001", 2.002", and 2.003".
No machining process is perfect. The size of the crank journal, the diameter of the bearing bore, and the thickness of the bearing are all going to vary a minute amount from the specification.
By matching a part (the journal size)from one group with a part from a corresponding group (of the bearing bore) they are able to achieve that .002" with more accuracy on all their engines.
By holding everything to tighter dimensional tolerances, you achieve better quality control and fewer failures. Honda started using this in the 60's or 70's and the American companies didn't start until the 80's.
I have no doubt that an American engine these days can last as long as a Honda engine. It is the fact that they have been making reliable engines longer that makes Honda have the reputation of reliability.