I'll bet the FSM means set the engine to 15* ATDC *before* removing the IP and leaving it at 15* ATDC when installing the IP. I hope turning the crank without something to keep tension on the chain in place of the IP doesn't mean another visit to the machine shop for a few new valves. There is an assembly tool that holds the IP timer sprocket in place when the IP is off but the tool attaches to the front cover. Come to think of it, how did you get the chain in place without tension in the IP timer sprocket?

Sixto
87 300D