The first thing you need to do is run a new 12ga. wire from the Bat terminal on the distributor to the fuse block or ignition that only supplies current when the ignition is on. I have a 70 Chevy 1/2 ton and installed an HEI and connected the 12ga. wire to the ign terminal on my fuse block.
The next thing you need to do is pull #1 spark plug and have someone tab the motor over while your finger is on #1 spark plug hole. Stop when the piston pushes the air out past your finger..."your at TDC". If you go too far the piston will be down in the cylinder and you'll have to sneak up on it again. I keep my eye on the notch on the harmonic balancer coming up on the timing tab. When you get the piston up on top then pull the distributor cap and the rotor should be pointing at #1 spark plug wire. If not then you have to pick-up the distributor and move the rotor and try it all over again until the piston is at TDC and the rotor is pointing at #1 spark plug wire on the cap. Then make sure of your firing order 1,8,4,3,6,5,7,2 . Should fire then.
Joe
