I believe you can log Inst. as well. Everything but PIC.
Don't ask me what reg this is... I'm lazy and pulled it off another website:
(b) Aircraft ratings. A flight instructor may not conduct flight training in any aircraft for which the flight instructor does not hold:
(1) A pilot certificate and flight instructor certificate with the applicable category and class rating; and
(2) If appropriate, a type rating.
No mention of endorsement.