US miles are identical to UK miles? I think so. 1 UK mile is 1.609 kilometer.
40 mph x 1.609 = 64 km/h.
86 mph x 1.609 = 138 km/h.
Assuming the limit at that place is only 40 for a reason, 86 was probably quite recklessly of you.
Doing the same offense in Norway would get you 3 or 6 months in prison and about $ 3000 in fines. And your license would be revoked for maybe one year, you would have to go to a driving school and do all that over again in order to get the license back.
Be glad you didn't do it here, it would have sucked more.