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Old 09-08-2002, 01:12 AM
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Post Mallory Dual Point

Hi folks,

I run a mallory dual point dizzy on a 350 Chev for short oval racing in the UK. We recently had starting problems which we tracked back to the dizzy. When it was stripped, one of the weight springs had become detached. This was refitted, but I noticed that the two springs are different weights!

Anybody know if this is correct? Also, as one set of points 'breaks' just before the other, does it matter if the heavy spring is first or second??

Cheers dudes,
Chuckie

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Old 09-08-2002, 08:32 AM
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I had a mallory dual point several years ago, I think the springs should be the same.
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Old 09-09-2002, 10:32 AM
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i think so too
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Old 09-09-2002, 10:46 AM
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Actually, there is no problem with the different size springs. If you look closely, the two cenrtifugal weights act on the cam plate as a unit. Thus the springs can be cosidered as a single spring for tuning purposes. In fact, if you could find the proper heavy spring, you could totally remove one of the springs and use just the heavy one. These springs are what determines the centrifugal advance curve for the distributor. Stronger springs delay the advance, weaker springs quicken the curve. Some tuners even fiddle with changing and grinding the weights that the springs are hooked to for customizing the advance curve. Variable spring size is a designed feature which allows fine tuning of the advance curve specifically by sizing the springs individually as is done in your distributor. This feature greatly extends the variety of springs rates available to the tuner, given a fixed number of springs.

Both weights operate on the advance plate just as they would on a single point or magnetic breaker sysetem. The dual points simply provide a mechanical way for the dwell to be extended a few degrees over that allowed by single points. One set closes and by time it would open, the second set has closed, stays that way for a degree or two then it opens too.

This is old technology. Modern electronic ignition systems eliminate the need of this mechanical (points - the weights and springs are still the best way to tune centrifugal advance.) system by extending the dwell with electronic circuitry. They do it better, longer, and with less chance for mechanical malfunction.

[ September 09, 2002: Message edited by: willys36@aol.com ]</p>
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Old 09-09-2002, 10:47 AM
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I have seen the Mallory distributors both ways, with both similar springs and obviously different springs. Have no idea why they have different springs, nor if it matters how they are installed.
As you noted one set of points begins to break before the other, this extends the dwell and is also the reason why the points should be dwelled seperately. Hope this helps.
Cheerio,
Bill
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Old 09-09-2002, 01:26 PM
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This is a common tuning trick, the side with the heavy weight and the heavy spring go together. Light spring goes with the light weight.

If both weights are the same then it doesn't matter.

[ September 09, 2002: Message edited by: 4 Jaw Chuck ]</p>
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