When removing the gear, be...
When removing the gear, be careful to support it on the smooth section while driving out the pin. Protect the teeth, which can be broken with impact. With the gear removed, the shaft can be pushed out. There may be a buildup on the inside of the housing. Clamp the body in a vise. Spray the shaft with WD-40. Then twist the shaft in and out until it comes loose.
Anytime the ignition is modified to eliminate ignition advance, obviously you will have full advance all the time. The ignition might be set on 36 degrees of advance. This would not be suitable for the street. However, most well-prepared racing ignitions have been set to have full advance by at least 2,600 rpm. On the track, the speed rarely drops to less than 2,600 rpm under load. This means that full advance all the time is not too bad. Sometimes a problem can occur when starting an engine with too much advance. A solution here is to use one switch for the ignition and another for the starter. Engaging the starter first, let the engine begin turning. Once the engine is spinning, turn on the ignition switch.
Now our distributor is finished. But before final installation, we must find Top Dead Center (TDC) of the piston on the compression (firing) stroke. If the engine is newly assembled, you probably degreed the cam and set the crank to have the No. 1 position on TDC before installing the intake manifold. This makes it easy to install the distributor.
There is one thing that gives many racers, even experienced racers, a tough time. With the engine all buttoned up, it can be difficult determining when No. 1 is on the firing stroke.
At the top of the distributor...
At the top of the distributor lies the advance mechanism. It mechanically controls the ignition timing relative to rpm. For a racing engine, this often works too slowly. Advance kits are available that have different-shaped weights and springs as shown to the left. Another option chosen by circle trackers is to lock the advance. This can be done by welding the two top plates together. However, the plates must be in the correct position to each other, or the rotor point may not align with the terminal in the distributor cap at the time of ignition. This can cause a misfire. A better way is to get an advance lock-out plate (arrow) made to fit over the pins and correctly locate the plates.
There are several methods of locating the position. To begin, there is, or should be, a TDC or zero mark on your crank balancer. There may also be other degree marks. The TDC mark will usually be the last mark to come to the pointer on a stock balancer when the engine is rotated. An aftermarket balancer that is fully degreed is a real plus. The mark on the balancer indicates TDC of the piston on the No. 1 cylinder. This may or may not be on the firing stroke. Because the cam rotates at half crank speed, it is possible for the ignition to be 180 degrees out of phase with the crank. Simply put, the cam is aligned on the firing stroke of the crank only every other revolution.
There are several ways to positively locate the crank-to-cam phasing with the engine already assembled. One of the easiest begins with removing the No. 1 spark plug. Cover the hole with a finger and rotate the engine. Compression force will blow your finger away from the hole. Now look at the balancer. You should be close enough to TDC to see the mark. This might take several tries. Rotate the engine back to the zero mark.
Now the No. 1 piston is at TDC with the cam aligned to be on the firing stroke. If the distributor were to be installed here, the spark would be retarded. Rotate the engine about 15 degrees in the direction it runs, if you have stock or near-stock advance curve parts in the distributor. If the ignition advance is locked, then rotate the engine about 35 degrees. Take heart if you don't have a fully degreed balancer. On a small-block Chevy, approximately 1/16 inch on the surface of the balancer (any size) will equal 1 degree. This is not exact, but it will be close enough to start the engine. Therefore, if you wanted 35 degrees of advance, you would measure off 23/16 inches from the zero mark on the balancer. Timing tapes are available that effectively convert a stock balancer to one that is fully degreed.
Drop in the distributor when the crank is fully positioned. Remember to turn the oil pump drive so the distributor tang engages it as the distributor gear meshes with the cam gear. If done right, the rotor will point to the No. 1 terminal on the cap.
It perhaps required a bit more effort than you thought, but now the ignition is right.
In photo A, I cut away a cap...
In photo A, I cut away a cap to show how the rotor can align or misalign with a terminal. When the shaft is turned, hard spots can be felt as the reluctor teeth align. At any one of these spots, the rotor must align with a terminal in the cap. An old cap cut away as shown makes this easy to check. However, it can be done by carefully marking the rotor and reluctor positions.
Photo B is an example of an...
Photo B is an example of an alignment situation in which a misfire is sure to happen.
These are the shims that should...
These are the shims that should be used if needed to establish distributor height in the block. If the distributor goes too deep in the block, it will bind against the oil pump drive. This can lead to both oil pump and ignition problems. Don't stack gaskets, but use these nylon shims (arrows). Stacked gaskets will compress, possibly allowing the distributor to rotate. How much clearance is necessary? Just have some!