300e timing marks won't line up. Valves seem to hit the pistons.
 

Did the headgasket on my 86 300e and put a rebuilt 89 head on it. When lining up the timing marks I lined up the balancer's "O|T" mark which is located between the 40-30-20-10-OT-10-20-30-40 marks and attempted to line up the two timing marks on the cam when it stopped and wouldn't go any farther. I turned the motor a bit then the cam aligned and the opposite happened, the motor wouldn't line up because it refused to turn at about the 20 degree mark.

What gives?

Get the pistons off the valves. Remove cam sprocket bolts. Turn cam so locating pin is on the right side of the engine (passengers side of the car, in other words line of the cam for #1 TDC). See if you can get the engine (pistons) to TDC. If not you will need to remove the cam bearing brackets again so the valves all close. With the cam at the timer mark and engine at TDC, you can then reinstall the cam bearing caps and bolt the cam sprocket on.
Gilly

If you can move the crank to ~ 45 degrees either before or after TDC you should be able to turn the cam without interference. Get it lined up first and then try to line up the crank to it. If that doesn't do it then pull the cam bearings.