0
That's a good question. For some reason, I was thinking the cost wasn't bad, but I can't remember if I even had a number in mind or if I just made that up.
Do the rough math on oil changes, air/oil filters, valve adjustments, spark plugs, carb work if not FI, any engine tuning work FI or not, replacement exhaust pipes, misc engine gaskets etc. No radiators to break, no radiator guards to buy. No shift lever to fail, or to punch through the case. Plus the time or money spent on labor. $3600 is a high bar for break-even, but never having to touch an engine in 500+ hrs sounds pretty sweet. 500hrs/20hr oil changes, which is probably a high interval for most, is 25 times. Add up the cost of misc. expenses on things like buying radiator guards or pulling out a dent on an expansion chamber, especially over say 5 years, and $3600 starts to sound a little more justifiable.