Best engine builder out there is yourself . You can buy the same parts they get , and then you can learn what is good and what is not working . You can get a head and carb combo from Voss or Jimmy Rivers or even Dover . Buy some tech tools , such as the height gauges and no-go stuff , a wheel to check cam , and some feeler gauges and a hone to square up the bore some . Get a rule book also . I am not knocking the builders out there , they have dyno's and all the fancy gadgets that they use , but to keep the costs down , you can do a lot by learning it yourself . You can build a good engine that lasts by using stock type rings that you file down or even low tension rings . But if you have to have an engine from a builder , make sure he is asking you the right questions as to what you want , and that you get the answers to the questions you are asking . Some builders don't like to tell you information , some do . Just remember , some , not all builders , only build engines to last only so many races before you have to ship it back to be freshened up . This is just my opinion as far as the best builder , but as stated above , setup and tires win more races than engines do .