Orient came from behind to record their fourth win in five games, but had to survive a second half battering from lowly Carlisle.
The visitors were given a dream start when defender Brian Shelley scored a contender for goal of the season, when he intercepted as throw from Orient keeper Scott Barrett and sent a 35 yard pile driver into the net.
However, Orient's response was almost immediate and they levelled when Barrett's long clearance was flicked on by Chris Tate and Jabo Ibehre squeezed between two defenders and lob the ball neatly over keeper Matt Glennon.
Orient played some impressive football, took the lead after 33 minutes when Tate retrieved a corner and whipped in a cross from the right for skipper Dean Smith to nip in and net form close range.
But the battling visitors almost levelled on half time when Mark Hudson thumped an effort from 12 yards against the bar.
Carlisle continued to press in the second half as they dominated for long spells and Orient keeper Barrett made a fine save after 62 minutes to deny Brian Wake.
As the Cumbrians threw more men forward the home side nearly snatched a third goal on the break as substitute Lee Thorpe forced Glennon into a smart save.
A relieved Orient manger Paul Brush said: "It was a good result, certainly better than the performance.
"We played with grit and determination and battled throughout, but I was pleased to hear the final whistle." While visiting manager Roddy Collins admitted: "We had lots of possession in the second half but it wasn't constructive.
"I can take heart from the amount of possession we had but I was disappointed with the way we defended."