I have over 10 years experience working for two different companies manufacturing performance speed equipment. Once a product becomes something that is a production piece, component or assembly like say an engine, there are all sorts of ways for quality problems to occur. From a cost standpoint building engines production style makes good sense over a small operation building custom engines one at a time. But once production and cost to produce enter the picture, quality and attention to detail will go down. If the only thing you want is a toy to make some noise and burn rubber, then a big cube crate engine will get it done but if you want something special that makes the most of the parts used, a custom built engine is the best way to go.
