flywheel timing mark

My Dodge 360 engine's timing can only be checked looking downward at
the flywheel from an inspection hole inside the van. The smog specs
call for 6 degrees retarded. Since there are no reference marks at the
inspection hole except for a "centering" line on the hole, can someone
tell me how many fractions of an inch I should eyeball the flywheel
indicator mark from "center?" I assume the smog check station also
have to approximate the mark. Last time I had the beast smogged they
had to check the timing by this method.

Any input would be appreciated.

Dick

 

Suggest you set the timing where the van runs well (6 degrees retarded
probably isn't it), buy the Mopar Performance timing tape and adhere it to
the damper in such a location as to indicated 6ATDC when the actual timing
is whatever you set it to.