Chain is slack and car won’t start

[Jonp123]

Hi guys, i’m new hear and am really in need of some advice. Thursday morning went out started the car it fired up as normal until revs dropped to idle speed. The car then began to shake uncontrollably almost to the point of stalling. ( i has to get to work so i drove approximately 3 miles and turned car off) Nothing unusual in normal driving conditions car was as smooth as always. went to work came home started car again. Shaking was worse, drove to my local garage, stopped at the traffic lights and decided to turn engine off due to bad shaking. Tried to start the car and nothing when light went green. i got the car towed to garage about 1 mile away. The garage inspected top part of chain and said they could lift it off cam as it was so slack. Any ideas if the car is salvageable? and where to take it to have valves etc checked? 

cheers jon