I have a bone-stock '72 Dart Swinger and I can't seem to find out what the correct timing should be... ANYWHERE. My dad says 5-6 deg., but that runs terrible. I bumped it up to around 12 deg. and it runs much better. Will that cause damage or can I run it higher still? (225 with Holley 1bbl)

Welcome on the board. The factory setting specification in a '72 is 0° (TDC) with the vacuum advance hose disconnected and its carburetor port plugged, engine idling at 750 to 800 rpm. With everything stock ('72 distributor, etc.) and in good condition, the engine will run better with a setting of about 5° BTDC. If you have to set it at 12° BTDC to get it to run decently, something's the matter — settings like that were factory stock on later slant-6s with distributors, carburetors, and emission controls configured differently than on your '72. Two things to check (it helps to remove all six spark plugs before doing both of these tests):

1. With use, the timing chain stretches and the camshaft timing retards. Because the distributor is driven by the camshaft, this retards the ignition timing, too. You can adjust the ignition timing by turning the distributor, of course, but that doesn't fix the retarded cam timing. To check for this, remove the distributor cap. Turn the engine by hand using the fan and belt in the direction of normal engine rotation until the distributor rotor begins to turn. Then turn the engine the other direction while you keep watching the rotor. If there's much of any perceptible lag before the rotor begins to turn, the timing chain has stretched and needs replaced.

2. The timing mark is located on the outer ring of the crank pulley, which is separated from the inner hub of the pulley by rubber. The belt groove is in the outer ring, too. Over time, the rubber-metal bond can let go and the outer ring can slip with respect to the inner hub. That makes the timing mark inaccurate. Specifically, it makes the mark show less advance than actual (for example, if the mark shows 5°BTDC, the actual timing will be earlier than that…might be 10°BTDC, might be 20° BTDC, might be something else, depending on how much slippage has occurred.) To check for this, straighten out a piece of coat hanger wire and insert it into the frontmost spark plug hole. Rotate the engine by hand until the coat hanger wire stops moving upwards/outwards. Check the timing mark. If it's nowhere in sight, rotate the engine further until the coat hanger wire once again stops moving upward/outward and check the timing mark again. It should indicate 0° (TDC). If it does not, the damper has slipped and needs replaced. They're not difficult to buy new.

Tune-up parts and technique suggestions in this thread. The engine will need periodic valve adjustment. Get the three books described in this thread as soon as you can. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

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