First find the spout plug, it will be near the TFI module. Loosen the distributor lock bolt, start the motor and let it settle down into a stable idle. Connect the timing light to the battery and #1 plug wire, pull the spout plug, and point the light at the balancer where the pointer is, you should see the timing marks. If the marks aren't visible shut the motor off and crawl underneath with some sandpaper to clean off the balancer. After wiping it clean rub some chalk over the timing marks and wipe with a dry cloth so the chalk remains in the marks and highlights them. With the motor running and the timing gun set to zero advance the pointer should be on 10deg, if the gun has advance adjustment and you set it to 10 the crank pointer will be at zero. This is the factory seting, but most motors will handle a bit more, 12-13 degrees, which will make the motor a little peppier.