[bodywerks]

It needs to be 28 degrees before top dead center.
Make a simple protractor where the center axis is the crankshaft and fix it to the crankshaft.
Remove the spark plug from the engine and plug it into the ignition lead.
rotate the crankshaft until you hit top dead center. You can do this by sticking a pencil or something similar (that won't scratch the piston) down into the spark plug hole and rotating the crankshaft until the pencil comes up as high as it will go. Now, there is a "dead spot" at TDC, where the connecting rod goes over center before it starts moving the piston again. When you get to that point, rock the crankshaft back and forth slowly and note, on each side of the rocking motion, where you see the piston move. The center of these two end points is your official TDC.
Now fabricate a pointer that points to the "zero" mark on the protractor while the piston is at TDC.
Now turn on the ignition and slowly rotate the crankshaft until the plug fires and note where the pointer is pointing when it does. Do it a few times to make sure.
The pointer should be pointing to about the 28 degree mark on the protractor. Plus/minus 1-2 degrees really doesn't make a world of difference for pump gas, so your timing has to be off quite a bit before you notice it.