The summer signing from Charlton opened the deadlock in the 65th minute but it took his 78th minute penalty to see off the Gulls after Tim Sills had equalised for the visitors.
The Eagles deserved their win though as they had completely dominated the opening period and could have been a couple of goals to the good inside the opening 20 minutes.
Victor Moses headed straight at Scott Bevan before the highly-rated youngster fired inches wide with Bevan beaten.
Neil Danns was next to try his luck but the former Birmingham and Blackburn midfielder whistled his shot past Bevan but back off the bar.
It was all one way traffic and Alan Lee got in on the act when he turned sharply in the box midway through the half but fired straight at Bevan.
New boy Ambrose also let fly from distance before the break with two shots from distance.
The first flew wide but the over-worked Bevan proved he was in fine form on the stroke of half-time as he got down to his left to keep out Ambrose's next effort.
On-loan Peterbrough striker Scott Rendell, who scored on his debut in the opening day win against Chesterfield, finally threatened for Torquay but Julian Speroni comfortably saved his effort.
But the Eagles pressure finally told in the 65th minute. Danns skipped away from two defenders on the left before looking up and crossing for Ambrose to head home his first goal since his move.
The lead last just nine minutes though as Gulls striker Sills stunned Selhurst Park with a brilliant header from Kevin Nicholson's cross.
But Ambrose and Palace stormed straight back and they were back in front just four minutes later.
Chris Todd fouled Alasanne N'Diaye in the box and Ambrose swept the ball past Bevan and despite late Torquay pressure that's the way it stayed.