I posted this in the garage area and then I discovered this area, so I will re post here.

I purchased a new timing chain and sprocket for an 82 dodge 1/2ton custom with a 318 engine. The sprocket has three alignment marks, why and which one do I use?
Sure am glad I'm not in a hurry to do this job.

 

Read the info on it,it may be one with a straight up mark and one for 4 degree advance and 4 degree retard.
Does it have 3 keyways?

 

nope just one key way. I can understand the 4 degrees retard and advanced but I could imply turn the distributor to get that.

 

The 4 degrees at the chain moves the cam advanced(which will help bottom end) or retarded not just the ignition timing.
Back to any paper work on the chain set.

 

Okay I understand about advancing the cam for or aft, but like I said from the beginning the gear and chain did not come with paper work and all my Haynes book info just tells me how to set it up on top dead center. I did not want to do the trial and error in this case but looks like I might have to try the 4 degrees advanced. Thanks for your help Moparborn.

 

The most likely reason for the multiple marks aside from the +/- is that the set will probably fir more than just your year. See if the manufacturer has a web site and see if they have the spec as to which one is for your particular year.