Ported vs Unported Vacuum for the Distributor - Why Not Have Both? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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  #16 (permalink)  
Old 11-21-2012, 09:25 PM
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Originally Posted by cobalt327 View Post
Your vacuum advance set-up results from the need for specific timing requirements under various conditions.

An example is when the engine is cold, the amount of advance allowed by the system will be different than when the engine is warmed up. That's why the vacuum lines are routed through various vacuum temperature switches, etc.

My advice would be to leave the system as-is. If the vacuum advance unit is faulty, replace it and leave the rest of the system intact unless you have a good grasp of the needs of the engine regarding the vacuum advance.

Should you want to experiment, remove and leave open the rearmost (#1 on the diagram you drew) vacuum port on the vacuum advance. Plug the hose.
Connect port #2 to a manifold vacuum source (full time vacuum, even at idle). If the line on it now is a manifold vacuum, leave it on. If it's not, plug it and find a source of manifold vacuum. Use a "T" if necessary.
See how the engine performs and pay attention to any signs of detonation (pinging).

Next, connect port #2 to a ported source and see how that is. Pick the best one if there's a discernible improvement. But I'd be surprised if there's any difference.

Now, that's not to say there's no way to improve what you have.

Sometimes adding initial timing helps performance, sometimes adding total timing helps, or both. But what you do not want to do is add initial timing w/o verifying the total timing isn't now too high. This is very important because too much total timing can damage the engine with detonation or cause you to have to use premium gas. Tuning it to run on premium is OK, detonation is NOT OK.

Read the section on timing here and see if it makes sense to you. If you grasp it, you might want to use a timing tape and timing light (or a dial back timing light) to plot the way the advance curve is now, and see if adding some initial or total timing helps, or bringing in the mechanical advance sooner helps. This is done by using lighter springs in the advance mechanism.

BTW, the part marked as a filter might be an intake air temp vacuum switch.
Here's a couple of photos showing the location on my intake manifold where the gas filter and the bimetal valve assy actually installed/tapped.


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Old 11-22-2012, 01:15 AM
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By "gas filter" do you mean that's what you believe is filtering the fuel to the engine? Because it's not doing any such thing. It has vacuum lines running to and from it, after all. It has something to do w/the intake temperature or possibly the amount of vacuum present.

But in any event if that's all you have after reading my post above, I believe I'm done here anyway.

Good luck.
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Old 11-22-2012, 02:44 AM
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By "gas filter" do you mean that's what you believe is filtering the fuel to the engine? Because it's not doing any such thing. It has vacuum lines running to and from it, after all. It has something to do w/the intake temperature or possibly the amount of vacuum present.

But in any event if that's all you have after reading my post above, I believe I'm done here anyway.

Good luck.
I didn't said nor infer that this "gas filter" is filtering fuel to the engine. By "gas filter" in my understanding is that it filters air going to the engine by virtue of a vacuum. The "gas filter" written on the photos is to co-relate it on the illustration and the illustration was lifted from the vacuum diagram below and is what i believe to be akin to the system am trying to grasp and understand. And since the diagram am presenting here is for vacuum piping then "filtering fuel to the engine" is out of the equation here.

From the catalog, Item 23265 is a gas filter #1



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Old 11-22-2012, 04:58 AM
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OK- no harm, no foul.

There are often filtration units used in vacuum lines, especially when the vacuum lines are connected to devices that have small orifices. Those filters are usually stand alone, i.e. they do not need to be threaded into the intake. These filters look like the image below.


Honda vacuum filter


If they want to call that part (23265) a gas filter, who am I to argue- except to say that if this is connected through to the intake to allow vacuum to pass through to the three ports, I would have called it a filtered vacuum manifold or port and leave the ambiguity of "gas filter" out of the description.


Before going further, will you verify that the direction of rotation of the distributor is really clockwise as you show below? Or is it actually CCW.

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Old 11-22-2012, 07:04 AM
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OK- no harm, no foul.

There are often filtration units used in vacuum lines, especially when the vacuum lines are connected to devices that have small orifices. Those filters are usually stand alone, i.e. they do not need to be threaded into the intake. These filters look like the image below.


Honda vacuum filter


If they want to call that part (23265) a gas filter, who am I to argue- except to say that if this is connected through to the intake to allow vacuum to pass through to the three ports, I would have called it a filtered vacuum manifold or port and leave the ambiguity of "gas filter" out of the description.


Before going further, will you verify that the direction of rotation of the distributor is really clockwise as you show below? Or is it actually CCW.


You are correct Sir, the rotation is counter clockwise. My apology for the wrong rotation direction. The image should look like this:

image
Does this mean my distributor vacuum advance is working Sir? This is the very first time i opened this distributor and saw what the vacuum does to inside of the distributor advance!
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Old 11-22-2012, 07:45 PM
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Does this mean my distributor vacuum advance is working Sir? This is the very first time i opened this distributor and saw what the vacuum does to inside of the distributor advance!
I would say yes, it is working going by what you've described.

In looking closer, it appears that your vacuum advance is actually TWO vacuum advances stacked one on the other. Originally I had thought it was more like the type of vacuum advance that had one side that would advance the timing when a vacuum was applied and the other side would retard the timing when vacuum was applied (see example below). I don't know enough about how your set up works to have an idea of why there's two vacuum chambers together, that BOTH advance the timing... interesting, though.

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