I few weeks ago i was driving my dad's 240 and it blew the timing belt on the highway, so i decided i would do the change since i have done it on my 740 before.
So, last night i was changing my timing belt on my dad's 240. After i marked the car for TDC on the camshaft, i decided to remove the bolt for the camshaft. But right before i went to remove the bolt, i ended up knocking it off TDC. Unfortunetly i forgot to put it back and i went ahead and removed the bolt. I didn't notice my error until after i took the drive belt pully completely off and noticed that the notches were way off. Well, being stupid and thinking i could correct my problem, i went ahead and put the bolt directly onto the camshaft pully and preceeded to move the camshaft. I figured i could move it back to TDC manually. However, i then noticed that i have to way of actually making sure that i'm on TDC now. SO here is my real question. How does one check to make sure that the camshaft is on TDC without being able to check the marks? I've already turned the thing a number of times trying to fix it but now i'm scared to even start it thinking i've knocked it way off.

I figure the only way to correct my problem is to try and match the marks on the belt. Is this true? I don't want to change the damn thing and then turn around and blow the engine when i start it.

Thanks for any help. Its been a long time since i've needed any.
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-Brandon at FSU '88 744ti 156k miles