About 2-3 lbs more then the wrench is set at.
You can figure it out at home, by placing two bolts in a vice, and putting washers and nuts on them, and torquing one WITH the adapter, and one WITHOUT the adapter, until you get the same torque value when compared, then just add the appropriate amount when you torque the heads/jugs.
IE: If you torque them both to 40 ft/lbs, then you add the adapter, and keep turning the wrench back, until it clicks WITH the adapter on. It will take about 2-3 lbs LESS then WITH the adapter, to achieve the same torque spec, as the leverage is longer.
“When the going gets weird, the weird turn professional....” ~ Hunter S. Thompson~
R.I.P. Rubberdown. 1971-2012