[patrickt]

I agree with Wayne. Go with the 20 degree limit, and start off with 15 degrees initial timing, so you have a total of 35, and see how she runs. Then tweak it up a bit from there to see what she likes. Double check that your TDC really is at TDC (using your piston stop). If there's any doubt at all about your timing marks then just ignore them and mark one line at 36 degrees BTDC (that will be exactly one tenth of the circumference of your balancer from your TDC point). Then just set it at that line at, say, 3000 RPM, run it; set it a little before the line, run it; set it a little after the line, run it; then put it where it runs the best. The actual number doesn't matter, you'll just learn that your best timing is maybe a hair past the line at 3000 RPM.