The 19mm and 13mm are loosened in a counter-clockwise direction. The directions in the 103 engine manual say to loosen the 19mm about 1/2 a turn. I personally feel that you need to back it off a bit more in order to get the 13mm to do it's job in tightening the belt. I also believe that by not loosening the 19mm sufficiently, you increase the risk of striping the 13mm when tightening it down. It's easy to do this anyway, so go easy when snugging down the 13mm.
My 2 cents.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.