WHEN? first vave job on 3.2 1986
 

Is there a certain mileage where it is good to do a valve job on a 1986 3.2?

When it burns more than a quart every 500 miles.
When it smokes on deceleration.
When people call you into the DMV for polluting.

But there is no fixed mileage at which it is necessary or "time". I have seen it done due to worn guides at anywhere from 60k to 160k on my buddies' cars.

George