Here is some information from another forum
Ok, so then it is 4 degrees before TDC. Great! If I'm infront of the engine, the marking tab is at the 4 O'clock position. I have to plug the timing light at plug wire 5 or 8, but since the tab is on the driver side, I put the timing light on plug 5. I did disconnected the vacuum like it says on the opeators manual. I had seen on more than one Hot Rod website, that there is another way to set ingnition timing for optimum performance on the 454, but the instructions are rather lenghty and I will need like two other people to help me, and I got no one but me myself and I. As it is, I had to go under the MH like four times to finally hit the bulls eye on the 4 degree mark!
