Determining top dead center
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==Before you begin== | ==Before you begin== | ||
| − | One of the first things that you will need is a | + | One of the first things that you will need is a degree wheel, this will tell you EXACTLY where you are at when you turn the engine over. You can take this picture of the degree wheel and have it blown up to a reasonable working size by your local photo copy center. A couple of ways to use it is to have it laminated or glue it to a piece of sheet metal or aluminum. |
[[File:Degreewheel1.jpg]] | [[File:Degreewheel1.jpg]] | ||
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*Max Advance | *Max Advance | ||
| − | *Since the vacuum advance control unit is a part of the distributor, the number of degrees of vacuum advance is specified in DISTRIBUTOR *degrees – NOT crankshaft degrees. When talking about these control units, it is important that you know whether the person you’re talking to *is referring to the distributor degrees, or if he’s talking crankshaft degrees. All of the listings shown in the following chart, and in any *shop manual & technical spec sheet, will refer to distributor degrees of vacuum advance. You must DOUBLE this number to obtain crankshaft *degrees (which is what you “see” with your timing | + | *Since the vacuum advance control unit is a part of the distributor, the number of degrees of vacuum advance is specified in DISTRIBUTOR *degrees – NOT crankshaft degrees. When talking about these control units, it is important that you know whether the person you’re talking to *is referring to the distributor degrees, or if he’s talking crankshaft degrees. All of the listings shown in the following chart, and in any *shop manual & technical spec sheet, will refer to distributor degrees of vacuum advance. You must DOUBLE this number to obtain crankshaft *degrees (which is what you “see” with your timing light). Thus, a vacuum advance control unit with 8 degrees of maximum advance produces 16 *degrees of ignition advance in relationship to the crankshaft. When selecting a unit for max advance spec, the total centrifugal timing at *cruise must be considered. Thus, a car set up to produce 36 degrees of total mechanical advance at 2500 rpm needs a vacuum advance control *unit producing 16 degrees of crankshaft advance. This would be an 8-degree vacuum advance control unit. |
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| + | *Max Advance @ “Hg | ||
| + | *This is the range of manifold vacuum at which the maximum vacuum advance is pegged out. In selecting this specification, you must consider *the vacuum produced at cruise speed and light throttle application. If your engine never produces 20” Hg, you better not select a control *unit requiring 21” Hg to work. | ||
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