Ignition Fine Tuning

The car has been fairly reliable and I’ve been able to enter it in a number of shows. However the gas mileage has been much worse than I expected and the car isn’t running as well as I would like. I decided it was time to start optimizing some of the carburetor and ignition settings. I decided to start with the ignition since I knew of at least one problem with it. When I had my engine rebuilt, the machinist said that the rubber on the harmonic damper had deteriorated and had allowed the timing marks to slip. He had remarked the damper for top dead center, but I never really understood why he didn’t just replace the damper. I ordered a replacement that is a copy of the old 427 damper. It took about a month to arrive, and came with a new timing pointer and an integral pulley for the fan belt. I was able to install the new damper without much dis-assembly. Initially I thought I would have to remove the radiator for clearance, but it turned out that step was not necessary. After I buttoned everything back up and checked the timing I learned that the machinist’s marks matched the new damper exactly. I still needed the replacement since the rubber on the old damper was continuing to deteriorate. But at least now I had reliable timing marks and could fine tune the ignition timing with more confidence.

While I was working on the damper I sent my original distributor out to be rebuilt. I also requested that the re-builder modify the advance curve so that full timing advance came in sooner. He interviewed me to learn as much as he could about my car, driving, and the engine combination. The timing specifications he built into the distributor are 16-18 degrees initial advance, 9 distributor degrees at 2900 RPM, and 6 vacuum advance degrees added at 15 inches of vacuum. He also installed a Crane XR-I electronic ignition conversion while the distributor was apart.

Once the rebuilt distributor arrived back at my house, I marked the positions of the current distributor housing and rotor. Then I removed the old distributor and installed the rebuilt one, being sure to line it up with the markings I had made from the old distributor. This ensured that my timing would at least be close to the old timing. That plan proved to be successful since the car started up at the first tap of the key. I connected my timing light and set the initial timing to 16 degrees. I may choose to advance it another degree or two after I get a feel for how the car likes the timing set at 16 degrees.

The good news is that the ignition system appears to be working fine. The bad news is that the engine still isn’t running as well as I think it should. I do plan to replace the rotor, cap, wires and spark plugs when I get a chance. I didn’t bother doing that along with the distributor since all of those parts have very few miles on them. But I think it still makes sense to replace them and confirm that all of the ignition system is in good shape. I also need to go through the fuel and carburetion system to ensure I don’t have any issues there. Even though the carburetor has no more than 1000 miles since it was last rebuilt I don’t feel that I can rule out the possibility of it having any issues.