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When doing a major tune up the importance of the of the distributor function is sometime neglected. This neglect is the reason that some Thunderbirds do not perform as efficiently as they should and is a primary contributor to over heating. If the ignition timing is not advancing or in some cases advancing to much an overheating condition will occur.
I will not go into the details of the function of the distributor or its specifications. The details and specs are thoroughly covered in the shop manual for each year. The '55 model is covered on page 61 and the specifications are covered on page 340. The '56 model is covered on page 73 and the specifications are covered on page 360.
Their are two common problems that I consistently observe that prevent the distributor from function properly. The most common is a defective vacuum advance mechanism (see article on vacuum advance mechanisms). The other is a frozen breaker plate that the points mount on. A frozen breaker plate prevents the timing advance past its initial setting of 3 or 6 degrees. The breaker plate should be free to rotate and the springs should pull it back to the retard position. The spark advance characteristics are controlled by two breaker plate springs, working against the distributor vacuum control diaphragm. the amount of spark advance obtained is determined by the amount of vacuum supplied to the distributor and by adjustment of the breaker plate springs.
Distributor timing must be checked and adjusted in two places. The initial timing is checked with the vacuum mechanism disconnected. Using a timing light set to 3 degrees BTC for standard and overdrive transmissions, 6 degrees BTC for automatic transmissions. The second and most important is best done on a distributor machine. This function can also be done with equal results by an experienced mechanic with a timing light that reads degrees of advance. Connect the vacuum mechanism and insure all connections are tight. Accelerate the engine to 2000 rpm the vacuum mechanism should advance the timing 13 to 14 1/2 degrees in addition to the initial setting of the timing. If it is an automatic transmission the total advance @ 2000 rpm would be 19 to 20 1/2 degrees. At WOT or about 4000 rpm the total advance would be 28 1/2 to 31 degrees. Increasing or decreasing the advance by adjusting the breaker plate spring tension. This can be accomplished with the adjustable spring post. Please refer to the appropriate shop manual for more refined details.
Most '55 and '56 owners will be surprised at how well their car actually runs when the distributor is adjusted to specifications. No need to install a '57 manifold, carburetor and distributor for full performance potential.