In the engine compartment, just below your windscreen you will see the identification plates. Look at the following website:
http://www.geocities.ws/renault_4/oval_plate.html
Also look at :
http://en.wikipedia.org/wiki/List_of_Renault_engines
Your engine number is on a plate on the side of the engine below your distributor on a left hand drive
Sorry I don't know if its a typical number, maybe someone else can help.
I just know that if the number on the oval plate is 1123 then its a 845cc and if its 1128 then its a 1108cc