@Marshall Oil in the engine compartment? ( above the tins???)
Maybe worth checking a couple easy bits - not involving pulley nuts or engine case.
Above the tins you only have a couple items that run oil above the tins, & that can splatter oil above your tins all over the compartment ( in your engine compartment).
- the two lines that run oil on a traditional VS build... ( line to & from external oil filter, and your breather line/ lines if you have a more complex breather system). Maybe one of them is loose- or has a cut/nick.... And under pressure leaks/ squirts oil out,,, the lines are right next to the belt/ pulley, And breathers is typically mounted against the fire wall / fwd of the engine in the compartment which can then help spray oil everywhere.
I DELETED the portion about the oil filter lines ABOVE... MY BAD. They run under the tins.
- or... your oil dipstick not in the hole. ( and when the engine is running oil is sputtering out. Again next to the belt/pulley, which could help spread the oil everywhere).
- also worth checking your oil cap is on tight... not loose.
Other than those lines, and your oil dip stick there is no other systems above the tins that could leak- spray oil all over above the tins. ( that I’m aware off... but I am not a mechanic, though I play one In my garage on the weekends ;-))
have you tried looking in the compartment with the engine running... with someone reving up the car to see if something “squirts out”.
a picture would help, if you want assistance identifying your oil lines, breather lines, and were your oil dipstick is located.