I have a Jaguar XKR 2000 super charged V8 AJ26s or AJ27s engine that broke a timing chain tentioner on start up. It did the classic chain break etc. I am replacing all tensioners and four timing chains etc. The front engine cover is off and all parts arer removed but the engine has only 15 degrees of movement and I cannot crank it by hand until it stops. The pistons all move up or down when I test this 15 degrees of movement. Why does it not rotate 360 degrees. More engine damage than I suspected?