Sure this has been asked a million times now. But I pulled a stupid. I didn't tdc the engine and make sure sprocket was lined properly to the head when I removed it. I marked 3 points on cam and chain to line it up. Then chain fell from its hook. Machine shop returned head with cam set to 12 o'clock. Everything is out of whack now. Do I now have to pull the main cover to align everything or can I figure back tdc and set sprocket with tool to get the alignment? Is ignition fired from crank or cam sensor. The Bentley book I got I think is crap for explanation.

 

The only sure fire way is to line up the colored links on the timing chain with the notches in the sprockets, which requires having the front cover off. There is not a TDC mark. In theory, a skilled mechanic should be able to use dial indicators and engine knowledge to find TDC manually, but that's about as much work as removing the front cover...

There have been some heated arguments about this. There is more than one way, you have to decide your appetite for risk, knowledge, skill, etc.

If you are doing engine work after something bad happened, it is always a good idea to check the oil pump (integrated into the cover) to make sure it is free of debris.

 

I understand there is a guide along the bottom of the crank sprocket on the cover. Is this close enough not to let the chain drop off the sprocket and out of time? I hate the thought of pulling that cover. It seems like major project while the engine is in the car. That's why I was hoping that TDC #1 and the cam mark would be the same. All the other cars I have worked with have it this way!

 

Yes, the housing is made to keep the chain on the bottom sprocket. But the timing marks on the two sprockets are not related to TDC. It would be up to you to get the engine and the head to TDC based on some measurements.