mechanical advanc vs. vacuum advance?

Old 02-08-07, 06:58 PM
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mechanical advanc vs. vacuum advance?

Hi again everyone. I have a 1968 Ford ranger with a 390 in it..I am wanting to get rid of my points distributor and go to electronic. I have found a good deal on a distributor with the electronic conversion in it. However it is a mechanical advance distributor and the one I have now is a vacuum advance. I am not very familiar with mechanical avances..does it require adjusting. That is why I want to get rid of the adjusting. Thanks in advance for any help!!
Old 02-09-07, 03:38 AM
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I'd keep my orginal distributor

and consider something like the Pertronix Ignitor II. They make them for most Ford models. Some searching should find what you need.
Old 02-09-07, 04:23 AM
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while you can change the advance curve on some models by changing out spring or weights, typicaly there is no adjustment you just set your base timing and your done and most stock distributers, have both a mechanical and vacum advance.
and while you posted about an hei for your ford 390 there is a few manufacturers that do make distributers for some ford engines with a gm hei ignition system however havent seen any for your engine but im sure there has been some made, you might check ebay as there is alot of the gm hei conversions sold on there fairly reasonable, just havent seen any for your specific engine, and im sure some ford lovers would never consider installing a gm distributer on a ford product but it was a good reliable ignition system for its time.

Last edited by bejay; 02-09-07 at 04:55 AM.
Old 02-09-07, 07:23 AM
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A vacuum/mechanical advance combination has certain advantages. The mechanical obviously advances relative to rpms with the centrifugal weights. The vacuum advance works relative to the loading of the engine. When the loading of the engine is light, the vacuum of the intake goes up and the vacuum advance is at its fullest. When you start loading the engine the intake vacuum reduces and the timing retards - to the point of the mechanical advance.

The advantage of this has to do with maximizing MPG while dealing with pinging issues in an engine under load.

In the more current systems, the MAP sensor takes that reading and instructs the computer accordingly.

I"m not sure how a fully electronic replacement for the combination would make that compensation.

Hope this helps,

Old 02-09-07, 10:39 AM
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Seriously - look into it. A easy drop-in conversion to your current distributor, and does away with the points. Affordable option.

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