No need for a fancy damper. You will need to do your own math. A typical 289 damper is 6-5/16" or approximately 160.5 mm. Take your diameter (measure with a tape is fine) times PI (3.1416). This is your circumference - or about 503.7 mm in this case. Divide this by 360. This gives you the mm per degree. Multiply by 30 and you get 42 mm for 30 degrees. Start at your zero mark on your damper and using string or a tape measure, put a mark 42 mm before zero for a 30 degree mark. Then put another mark at 56 mm and this will be your 40 degree mark. Now with the timing light check to see your total timing (with vac hose disconnected) compared to those marks. Adjust distributor to fall in between which will be 35 degrees. Now, also with the hose disconnected, see where your idle timing is. For example, if it is 10 degrees, in the future, this is where you would set your timing at idle to get the proper max mechanical timing for your distributor.
While out used for typing correction fluid or some narrow reflective tape would be a good way to mark your damper.
All of the values were based off of a 6-5/16" damper. Make a simple spreadsheet and re-calculate if if your diameter is different. A simple ratio work. If your damper is 7", take 7/6.3125 and multiply that by the two numbers above of 42 and 56. All you are trying to do is get in the ballpark so tape measure marks will be more than adequate for what your are trying to do for now. It is more important to get your max mechanical timing right than your idle. Today, for most distributors with 20 to 26 degrees of mechanical advance, 6 initial is a little low. Many run 10 to 14 degrees with no problems and get better performance and slightly lower temps.
Let us know where your idle ends up after this. Now that you know the actual timing, if you want to try 38 degrees max mechanical advance, you can take your known idle and add 3 degrees. The range for 289 iron heads may fall between 32 and 38 degrees depending on your engine combo. The internet doesn't know what your fuel is like and the condition of your engine. This is why you must test your engine to see what it likes.
Don't start changing any springs, etc., until you know what you currently have. Find your baseline and then you can investigate changes in the future.
You may want to do some research on valve float. Valve float is sometimes confused with a fuel or timing related miss. When you hit a certain RPM, the valve springs can't keep the lifters properly compressed and your valves won't fully close. The engine won't pull past this RPM and if feels like a miss. The older the engine, the springs start to lose stiffness and the RPM where float begins will drop.
Anyway, I digress. Start with good timing settings. I suggest getting your timing set before any more carb adjustments. Right now you have two unknowns. By getting the timing set, you will have only the mixture left to play with.
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GPatrick wrote:
