Pertronix and Timing - Team Camaro Tech
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post #1 of 7 (permalink) Old Mar 30th, 06, 09:28 AM Thread Starter
 
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Question Pertronix and Timing

I recently swapped out my points with the Pertronix Ignitor II(part #1181) and Coil. Installation was fairly simple and my car started right up. Now my question is how to set the timing with the Pertronix installed. Just from reading past posts and reference material, I know that total timing should be 34-36, but I am not sure how that is achieved. I undertand that a portion of the timing(8-12) comes from "initial" or "static" timing which is determined by shooting the timing gun at the harmonic balancer and twisting the distributor while the car is idling. The portion of timing that is determined by Vaccuum Advance and Mechanical is where is where I get lost. I do not need detailed explanations of this, but what I do need is what adjustments do I need to make and how to do it with the Pertronix installed. I have read that the gap between the magnetic ring and electronic module determines the dwell. The install instructions recommneded that the gap be anywhere between .010 and .060 and that's where I have it. I have a timing gun that has a dial on the back side of the unit. Do I need any other tools or gauges to make that adjustments that I am looking for? Here's a little info on my setup: 396(mainly stock), very mild cam, Aluminum Intake, Stock Q-Jet Carb, 10:1 compression. I am no mechanic and this may be well over my head. Thanks in advance for any suggestions.
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post #2 of 7 (permalink) Old Mar 30th, 06, 10:21 AM
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Re: Pertronix and Timing

Engine at idle rpm with vacuum advance hose unplugged is intial timing.

Run engine up in rpm's, usually 3500 rpm, and notice the amount of degrees of movement = mechanical advance. This advance is controlled by springs and weights underneath the rotor.

While at 3500 rpm's, hook up vacuum hose and record the change in degrees from the mechanical figure. This is the advance caused by vacuum.

Add all three figures up and you get total advance.

The only disadvantage is OE mechanical advance is usually set for it to be all in at 4000-4500 rpm. Using weaker springs, from the aftermarket, will lower the rpm value bringing mech advance to happen sooner.

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post #3 of 7 (permalink) Old Mar 30th, 06, 01:48 PM
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Re: Pertronix and Timing

Run a forum seach for ping curve

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post #4 of 7 (permalink) Old Mar 30th, 06, 02:17 PM Thread Starter
 
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Smile Re: Pertronix and Timing

Let me see if I understand.. Say if I set my initial timing to 10. Then I rev the RPM to 3500 or so and I check the Mechanical timinig at that point. I assume that I will use my timinig light and adjust the dial until the timing mark hits zero. If the timing gun is set to 20 and the timing mark is at zero, then the mechanical advance is 20. This is added to my initial of 10 to give me 30.

To determine the vacuum advance, I plug in the vacuum advance hose while the RPM is at 3500 and note the change. If the change is +5, then this number is added to my initial(10) and mechanical(20) to give me 35. Is this correct?

What is the optimum number for each value: Initial, Mechanical and Vacuum? Does it matter if initial=15, Mech=15 and Vac=5?

How is Mechanical Advance adjusted? In your statement you mentioned springs. Assuming that you are checking the timing at the same RPM, will softer springs increase the value and firmer springs decrease the value? Also, will different springs affect initial timing?

Back to the Pertronix question... Will differences in the gap between the magnetic ring and electronic module affect any aspect of timing?
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post #5 of 7 (permalink) Old Mar 30th, 06, 04:44 PM
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Re: Pertronix and Timing

You have the concept down good.

Spring stiffness and weight weight determine how soon/late the advance comes into play on mechanical. Soft springs/heavy weights timing comes in quicker and vice versa. there is susally a chart given with weight package to guide you through the process. Springs should not effect initial timing as rpm be too low to "bring in" mechanical timing.

Vacuum timing is used when engine rpm is low, such as cruise. Vacuum level will be high bringing in vac advance. At WOT (wide open throttle), vac adv is not present.

Some will hook up full-time vacuum to the advance cannister to bring in advance to help engine run better. Any throttle is opened, vac adv decreases until throttle is closed.

Unless you remove distributor and have a shop tune it, trial & erro is the only method. Having advance and engine not ping upon accelleration is the key.

Distance between the reluctor and pickup coil determines the amount of coil saturation, the amount of energy coil builds up to create spark energy, otherwise known as dwell time. The closer, the better, but not less than manufacturer recommends.

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post #6 of 7 (permalink) Old Apr 1st, 06, 06:55 PM
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Re: Pertronix and Timing

Quote:
Originally Posted by Golden69
Let me see if I understand.. Say if I set my initial timing to 10. Then I rev the RPM to 3500 or so and I check the Mechanical timinig at that point. I assume that I will use my timinig light and adjust the dial until the timing mark hits zero. If the timing gun is set to 20 and the timing mark is at zero, then the mechanical advance is 20. This is added to my initial of 10 to give me 30.

To determine the vacuum advance, I plug in the vacuum advance hose while the RPM is at 3500 and note the change. If the change is +5, then this number is added to my initial(10) and mechanical(20) to give me 35. Is this correct?

What is the optimum number for each value: Initial, Mechanical and Vacuum? Does it matter if initial=15, Mech=15 and Vac=5?

How is Mechanical Advance adjusted? In your statement you mentioned springs. Assuming that you are checking the timing at the same RPM, will softer springs increase the value and firmer springs decrease the value? Also, will different springs affect initial timing?

Back to the Pertronix question... Will differences in the gap between the magnetic ring and electronic module affect any aspect of timing?
Hold it - let's start over. When you set the dial at 20* and the timing index on the balancer is aligned with "0" on the tab, that's 20* advance, which INCLUDES the initial timing you set at idle; whatever you see on the dial with the marks aligned is TOTAL TIMING - the sum of initial plus the centrifugal the distributor mechanical advance system adds. That's the 34*-36* figure you're looking for with the centrifugal advance "all in". Vacuum advance has nothing to do with TOTAL TIMING, as it drops out when you put your foot down.

You check the vacuum advance operation at idle. If you have your initial timing set, say, at 10* (vacuum advance disconnected and plugged) and then connect the vacuum advance, the timing should jump to 25*, as the vacuum advance will add about 15* at idle vacuum (if you have it connected to manifold vacuum and it's the correct vacuum can for your application). That increase in timing will also increase the idle speed, so you'll have to set it back down with the idle speed screw on the carb throttle lever.

A good baseline to start from is 10*-12* initial, 24* in the centrifugal in the distributor, "all in" by 2800 or so, and a vacuum advance can that adds 15* and is fully deployed against its stop at 2" Hg. less than your idle manifold vacuum reading.

The Pertronix unit has no effect on your advance curve, and the gap between the ring and the module has no effect on your timing, assuming it's within Pertronix gap specs.

Weaker springs will bring the centrifugal curve in earlier (lower rpm), stronger springs will bring it in later (higher rpm). Properly-calibrated springs will not permit any centrifugal advance at idle rpm; you can check this by putting a rubber band around them and checking timing with and without the rubber band in place - it should be the same.

E-mail me ([email protected]) and I'll send you my "Timing 101" paper - it'll take the mystery out of this stuff and explain it in layman's terms. It's here on the site somewhere, but I don't recall where.


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post #7 of 7 (permalink) Old Apr 4th, 06, 12:02 PM Thread Starter
 
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Re: Pertronix and Timing

Thanks JohnZ.. I will email you requesting the instructions.
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