Looking for the best way to set timing. Currently I just set the initial timing to 11 deg. (I think that is correct for 71 Cutlass 350). I came across something called Total timing which is set timing to 36 deg. at 2500 to 3500 or whatever the RPM is when it stops advancing. Then if you check timing at idle, you can then calculate the timing range. So, what should the timing range be. If it is not 25 deg, should I make changes in the distributor mechanical timing mechanism.

 

If you have the factory original distributor then you have the timing set correctly.

 

Your timing should be 12* initial @1100 rpm with vacuum advance disconnected. If your engine is stock and your not racing it, stick with the factory settings.

 

But if you have any upgrades your timing will need to be adjusted to support those upgrades. There are a lot tutorials on YouTube and on the internet that'll help you out in better understanding your timing needs.

Also check your spark plugs out regularly to ensure they are in the proper heat range and your fuel mixture isn't either to rich or to lean.

 

To answer your other question here is a good read:
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf

And this:
http://www.lbfun.com/warehouse/tech_...101Article.pdf

And this:
http://www.lbfun.com/warehouse/tech_...%20ADVANCE.pdf