This is a little how-to for setting the initial ignition timing on a small block Chevy before its ever been run.
Note* this post assumes that you already know how to time a running engine, just not one that never been run before or has had its distributor removed and its timing settings lost.
**Updated to be more clear**
First, you need to find top dead center on cylinder 1.
This is simply done by removing the spark plug from cylinder one and putting a finger over the hole. Then slowly turning over the engine with a long wrench or breaker bar on the harmonic damper bolt and feeling for when air stops blowing out of the plug hole. When it stops, you should be near TDC. Finally, use the timing mark on the harmonic damper and align it with the pointer on the engine to get it perfect.
Cylinder one is now at TDC.
Next is to take off the distributor cap and aim the rotor at cylinder 1.
If you recall, these distributors don’t care which post you use for what cylinder as long as they are in the correct firing order, so, you can choose which distributor post to use for cylinder one. Generally, we try to aim the rotor so its pointing in the direction of where cylinder one is physically on the engine. It just makes more sense this way rather than using one of the posts at the back.
You may remove your distributor completely from the engine to align the rotor by hand if its 180 degrees away from the post you will be using for cylinder 1. You will also need an oil pump priming tool to rotate the gear on the oil pump so that the rotor can align properly. Once the distributor is re-installed and the rotor is pointing in the direction of cylinder one, you need to be sure that the rotor and the post are closely aligned as possible. That is, the rotor should be aimed directly at the post for cylinder one under the cap.
To help with this, use a marker and put a mark on the cap to note which post is the one for cylinder one. Make sure this mark is aligned perfectly with the post. Now, when you slip the cap over the distributor, you can kind of see where the post is aiming. Also, make sure that the distributor is bolted down enough where it can still turn, but doesn’t turn freely.
There is quite a bit of margin of error here. If you are +- 10° near where 0° should be, you’ll be all-right on most engines.
Congratulations, the engine is now timed to ZERO degrees, or at least close enough. But you probably wont be able to start the engine with this little timing; to start it, you will have to rotate the distributor by hand counter-clockwise to advance the timing until it fires. Its always nice to have a friend help you with this because they can crank the car while you advance the distributor. Of course, use a timing light to properly set the timing once the engine is running.
This method can be used to start an engine that has some sort of after market digital fuel injection system as well. It is recommended to set a 10 degree advance offset for the Chevy HEI 8-pin system. Your ECU should have a location where to set this offset, and once this is set, this location will become the new zero. This is done to make sure the rotor doesn’t get too far away from the post at higher RPM’s when the timing becomes more advanced and where charging a single coil becomes an issue. Just make sure your ignition table in the ECU is matching what the timing light is saying after things get going. Adjust as necessary.