One of my best mates is an engine builder and developer for a small but highly regarded local company who supply engines to the BTCC, DTM, F3 etc. He has no formal qualifications, just an engineering mind, is a little geeky and has a keen eye for detail. His job only came about as he was looking for a change of career and another mate who already worked for the company put him forward as he was leaving to go into F1 creating an opening and the company owner gave him a go starting on a low wage.
He gradually did different duties, proved himself over time and for the past 4+ years has worked on the Team Dynamics Honda BTCC engines, attending every race meeting and test, he's continually developed the engines and when not at the circuit has built and refreshed the motors. Must be doing something right as they won the championship two years running. This year however they are struggling against the turbo diesels. He's earning reasonable money nowdays but often works away from home, plus job security can be an issue when sponsorship deals and what manufacturers equipment or suppliers people use change every season. Theres lots of weekend work, both racing and testing and alot of stress if your team is leading a championship and an engine you built doesnt perform or worse lets go. Get onto an international championship and the travel thing can get even more silly, sounds glamourous but you have to really want it to live like that.