10.3:1 i believe..
well it depends on "1300 pistons", as there are 1300LC, 1300HC, and 1300GT..
the lowcomp pistons in a 1600 is 9.5:!, highcomp generates 10.3:1, and gt brings 11:1.
source: http://spannerfodder.com/the_works_escorts-xflow.php bottom of the page