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Pertronix and Vacuum

Mosesatm

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Joined
Jan 18, 2005
Messages
9,011
I just installed a Pertronix module and coil and now the car doesn't like to start as easily as it did. It used to start after one revolution, but now I must crank it 6, 7, or 8 times before it starts. Any ideas?

Also, does anyone have a diagram that shows where to run the vacuum lines to the distributor? On the forward port I have a line that comes from the forward vacuum distribution block but is also teed into the rear block. The rear port on the distributor runs straight to the forward block. With that setup the rear port is receiving much more vacuum at idle than the forward port, which seems correct to me since the vacuum should only kick in under acceleration.
 

rvrtrash

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Apr 25, 2003
Messages
3,649
Hey Arlie, my '68 only has a single advance dist. but here's some info to sort through in case you can use it. On my CS, the hoses to the vac. tee in the thermostat housing are: Top port to carb, Middle port to dist., Bottom port to intake. On a '69 I have with a dual advance dist., front port goes to the carb., with a delay module in the line and rear port goes to the intake. Hope I'm not confusing the issue even more.

Steve
 
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Mosesatm

Mosesatm

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Jan 18, 2005
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Thanks Steve. When I get home I'll see how the '69 setup works.
 

CougarCJ

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Jul 17, 2006
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2,186
Got 12 volts?

One thing that I found out over at my other favorite car site; Pertronix like a full 12v supply. We have found out that there is considerable less voltage if you use the wire at the coil.
I have yet to wire mine to a full 12v, but I have a friend with a 1968 428CJ car that picked up a full 1/2 second in the quarter, by just doing this simple change.

One thing to point out, this is for a Cougar XR7 and they have a factory tachometer. I am not positive or not if the tachometer wiring causes a voltage drop because of the resistance wire or not.

Check if your positive 12v wire is giving a full 12v when cranking.
 

rvrtrash

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Apr 25, 2003
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CougarCJ said:
One thing that I found out over at my other favorite car site; Pertronix like a full 12v supply. We have found out that there is considerable less voltage if you use the wire at the coil.
Check if your positive 12v wire is giving a full 12v when cranking.

That's a good point. If I recall, the coil power wire only has 8 or 9 volts on it. When I converted my '69 XL convertible to "factory" electronic ignition (components from a '76 truck) I had to run two wires from the starter relay to the ignition module to get the correct voltage. I'm suprised though that Pertronix didn't build it to work with the voltage that was available.

Steve
 
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PNewitt

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Hi Arlie,

Since you asked for "distributor vacuum line diagrams" maybe these will help. These are for 1968 Fairlane, Falcon and Mustang; 289 (302) with Thermactor.

If you need something different, let me know, and I'll find it for you.

Paul N.
 

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Mosesatm

Mosesatm

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Joined
Jan 18, 2005
Messages
9,011
PNewitt said:
Hi Arlie,

Since you asked for "distributor vacuum line diagrams" maybe these will help. These are for 1968 Fairlane, Falcon and Mustang; 289 (302) with Thermactor.

If you need something different, let me know, and I'll find it for you.

Paul N.
Wow, that's perfect!!

Thanks Paul
 
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PNewitt

Guest
You're welcome, Arlie.

If anyone else has a specific need/problem for a diagram I can usually find it and post it.

I will be including several of these type of diagrams for reference, in the book. This will make things a lot easier. If I find a corresponding line (T-Bird, Torino, etc.) that uses the same part, I might be able to list that, too, so you can find it in a junkyard, NOS, or as a service part.

Paul N.
 

p51

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Joined
Aug 2, 2005
Messages
1,025
Location
NorCal
Mosesatm said:
Also, does anyone have a diagram that shows where to run the vacuum lines to the distributor? On the forward port I have a line that comes from the forward vacuum distribution block but is also teed into the rear block. The rear port on the distributor runs straight to the forward block. With that setup the rear port is receiving much more vacuum at idle than the forward port, which seems correct to me since the vacuum should only kick in under acceleration.
Regarding how the vacuum should be hooked to the distributor, here's a general article on setting timing that I found useful...

http://www.centuryperformance.com/timing.asp

The interesting part about hooking up the vacuum is in the following...

"It is our recommendation that when you are using vacuum advance distributors, that you connect the vacuum advance to "full manifold vacuum". There are two schools on where to connect the vacuum advance line. On older applications the connection point was to "ported" vacuum. Ported vacuum means the port is drawing vacuum "above" the throttle blades in the carburetor. This means that as RPM increases, vacuum increases and in turn, vacuum advance increases. This was fine on older applications with high lead fuel and other ancient engine designs. Using this set up today can cause detonation problems, overheating, and other grief.

With our suggestion of using the vacuum connection to full manifold vacuum, the port will be drawing vacuum below the throttle blades. A good running street engine will have a measured vacuum at idle between 14"-20" of manifold vacuum. Now, this will give you a ton of advance at idle, but as load increases (vacuum drops) you will take timing away. This is excellent for the faster burning fuels offered today as well as in the fact that when you put your foot into the throttle and get the RPM building, you DO NOT need or want additional timing. On a RV or tow vehicle, when you put your foot into the throttle and downshift to climb a grade, you DO NOT want added timing that will slow the vehicle and add heat. You want the added timing for subtle throttle response, and low load engine efficiency. So, when you are cruising at freeway speeds or in town traffic, you have the added timing to save fuel, add throttle response, and overall give you a better feel."...

From this I gather that depending on whether you hook to the vacuum above or below the throttle blades you either advance or retard the timing when you open the throttle up. On my distributor there is only one vac hook point. Sounds like on yours there's two points - one to hook an "average vac" (teed pt) and one for full manifold vac.



 

390cs68rcode

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Joined
Dec 29, 2004
Messages
2,864
Location
Houston Texas
CougarCJ said:
One thing that I found out over at my other favorite car site; Pertronix like a full 12v supply. We have found out that there is considerable less voltage if you use the wire at the coil.
I have yet to wire mine to a full 12v, but I have a friend with a 1968 428CJ car that picked up a full 1/2 second in the quarter, by just doing this simple change.

One thing to point out, this is for a Cougar XR7 and they have a factory tachometer. I am not positive or not if the tachometer wiring causes a voltage drop because of the resistance wire or not.

Check if your positive 12v wire is giving a full 12v when cranking.

not sure if this gonna help I went through this on my 68 CJ. We went from a non original coil back to original and had a problem about cranking/running. We were not getting enough spark. My mechanic used a external resistor with the original coil and it seems to work fine now.

I bet you are not getting enough spark.
 
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