On my car there are no punch marks on the cams. There is a hole drilled in the cams. To get TDC you set the hole at 3 o'clock. There is no need to remove the cam cover the hole can easily be seen through the with the oil cap hole. You can see the hole long before TDC so there is not a problem using this method. There may be punch marks on your cams there are none on mine; the procedure says there are marks. If you want a post by Marshall Booth and Ned discussing this go to Okiebenz there are several post about this. That's the way I found out also the cam timing procedure show this too.