Just figured I would post this for those who don't know. If you have no timing light at your disposal this trick works. When you are stabbin' your distributor and you have your #1 cyl. at TDC (power stroke) and your rotor pointing where you want it, turn your crank backwards a little bit (against normal rotation) and bring it back to where the mark inicates the amount of advance you need (say 4 degrees BTDC). Note: you must go past the point where you want it and bring it back to where you want it, this will compensate for any slack in the chain. Next with your cap on and ready to run, take the #1 plug wire with a plug in it and lay it against a ground. Then turn on your ignition (don't start) with your ignition on turn the distributor against rotation slowly until you see the plug fire. Stop as soon as you see the spark, tighten your distributor and your set. I have done this and checked it with a timing light right afterwards, most times it's still right where I set it. With big cams (higher idle than stock) I noticed that it read a little more advanced as the centrifiguls were starting to open up.