Advanced diesel engine manufacture?

I would say he does not know what he's doing unless he was working on a race car. Some cars can have the cam gear moved ahead by that much for instance Toyota four runners have cam shafts with three marks on the cam shaft so that you can retard or advance the timing as needed for emission controls. However now days the car engine is computerized and the firring can be advanced or retarded by as much as 50 degrees to stop engine knock or engine pinging due to carbon build up in the combustion chamber. Normally on electronic engines the timing gear is marked, and so is the cam so that you line up the marks to make sure the cam is in time, so it would be set to zero on timing, the computer and the knock sensor would then determine what the best timing was for power and emission controls along with other parameters that are received by the power train module.

Since most cars no longer have distributors you can't advance the timing by loosening the bolt on the distributor shaft and advance or retard the timing to get the best possible results for running the car, now the computer does it all with sensors on it. Now that I have said that some mechanics would advance or retard the timing by moving the cam gear ont tooth off from base timing set. So new cars you can't do it to only ones with distributors can be advanced. Not only were you able to advance the timing of the distributors the distributors had a vacuum device on it so that when the engine had more vacuum it could change timing to save fuel or deliver more power as needed by determine if the engine was under load going up hill or down hill.

Just wanted to say you can't move the cam and crank marks to much one way or the other because on some engines you could get the valves to hit on close tolerance engines so really the only thing a mechanic would do is advance the timing on older cars, new cars you can't, On Diesel trucks you still can but you have to be within emissions limits normally the cam can be advanced 1 and 1/2 or 3 and 1/2 degrees per tooth but is a generalization it can very from manufacture to manufacture. hope this helps.