I have a Pertronix dizzy and I also run a Crane Hi-6 ignition. I have noticed that the cap and rotor seem to wear prematurely. I contacted Pertronix and they said, going by the pics I sent them, that the vacuum advance looks like it's rarely used. I run 18* initial and 34* total. I have the vacuum hooked to manifold vacuum. I run 4.10's and a Powerglide. The car runs between 2000-2500rpm and when on the highway between 3000-4000rpm. In the pics I included you will see that the rotor seems to be firing on the trailing edge. Pertronix says this is because as the vacuum advance pulls vacuum, the rotor rotates toward the leading edge. The pics show the trailing edge wearing more than the leading. I am thinking that the vacuum can may be beginning to fail because the can should be pulling by 2000-2500rpm. They said I can send the dizzy to them and they can phase it to where the rotor fires more toward the middle and leading edge, but I think something may be wrong with the vacuum can. I did notice that when I placed a hand vacuum pump on it, it got to around 20-25hg and you could hear the engine start to pick up RPM. I get 15-16hg of vacuum in park/neutral and 12hg of vacuum at idle in drive. If I rev the engine, you can watch the vacuum go up toward and past 20-25hg of vacuum and that is just at around 2000-2200rpm. What would you guys suggest? Take a look at the pics I included and let me know what you think. Thanks guys.
http://i61.photobucket.com/albums/h69/charliek3006/CapandRotor003.jpg
http://i61.photobucket.com/albums/h69/charliek3006/CapandRotor002.jpg
http://i61.photobucket.com/albums/h69/charliek3006/CapandRotor001-1.jpg

My thoughts are you are seeing the results of higher secondary voltage - the arcing across both the rortor and cap terminals.

Plus, the ionization of dist air inside the cap, there is no ventilation. you don't see these effects with a HEI cap & rotor.

The vacuum reading goes up because the throttle plates are closed further.

Guys: The rotor trigger looks like it is arcing on an angle.... What would cause that, perhaps a bad bearing in the dizzy.

The arcing at an angle is what I was referring to. Pertronix says it's wearing like that because normally a vacuum dizzy fires on the trailing edge of the rotor and as the vacuum advances it, the rotor rotates to fire toward the leading edge. That is why he said my vacuum is not used often because it looks like the rotor is not spinning to fire toward the leading edge. He says it's normal for the rotor to fire on trailing edge to start because as the timing advances from the vacuum, it makes sure there is always a part of the rotor to fire to the cap. I think with the cam I run(performance) and having to run 18* initial, it sets the rotor farther toward the trailing edge than normal. The rotor spins clockwise so in that picture, it shows the trailing edge being worn. He says that if my vacuum advance was being used, the rotor rotates and the middle and then the left side or leading edge begins to fire and wear. The only reason I can see as to why the rotor wouldn't rotate is due to a defective vacuum can.

Charlie that cant be a good thing, can it?

You would think that if the spark had fired on the majority of the rotor, it would get a better spark to the wires and plugs.

What Mr. Petronix suggests is true, the rotor is firing on the edge. But the erosion of the rotor and cap terminals is due to higher than normal voltage, thus, heavier arcing.

Its like the amount of arc between a 12 volt arc and a lightening bolt. This is the action causing the erosion.

What Mr. Petronix suggests is true, the rotor is firing on the edge. But the erosion of the rotor and cap terminals is due to higher than normal voltage, thus, heavier arcing.

Its like the amount of arc between a 12 volt arc and a lightening bolt. This is the action causing the erosion.

So do you think the amount of erosion you see is normal for a system with a msd type ignition system? Also, about the vacuum advance. Is it possible that the can isn't working to spec? I would think that at 2000-2500rpm, the can should be pulling in at least 20* of advance. That would make the timing at least 38*(18* initial and 20* vacuum), not to mention what the mechanical is. It's limited to 16*, but at 2000-2500rpm, it should only be swung out about 3-5*, if that. My mechanical springs are all in by 3500rpm. Given that and the 18* initial I run, do you think the erosion is taking place in the correct position? Should I test the vacuum can? If so, how? I put a hand vac pump on it and you could hear the engine RPM's increase. The vacuum pump was at 20hg. I don't know what the RPM's were. I have a tach for engine testing. Tomorrow I am going to hook it up and also hook the vac pump up and see what the RPM's go to and at what HG they do it.

Charlie that cant be a good thing, can it?

You would think that if the spark had fired on the majority of the rotor, it would get a better spark to the wires and plugs.


Skip, the reason ALL VACUUM ADVANCE dizzy's fire on the trailing edge is because as your vacuum advance begins to advance the timing, the rotor has to turn toward its leading edge. If it were firing in the middle, when the vacuum advance began to advance the timing, it would spin the rotor past the leading edge and the spark would have no path. ALL rotors fire on the trailing edge, unless you run a non vacuum advance dizzy, but on the street it's a must. For someone not running a vacuum advance, the rotor is setup originally to fire more toward to the middle.

All I am concerned with is whether or not THIS amount of erosion is normal for an ignition system that runs a mulitple spark setup? Also, if I should be looking at the vacuum can as possibly beginning to become defective? Thanks guys.

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#11 03-12-2008, 04:01 PM
msdtechsupport3
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There are a few reasons that could have caused the above failures. Excessive secondary resistance, poor contact with the rotor, cracked/damaged carbon ball (which could have occured during shipping or production for that matter) are just a few possibilities.

As for the corrosion, it varies considerably from region to region. The combination of air moisture and the ionization produced by the energy arcing from the rotor tip to the terminal for the spark plug wire tends to oxidize the zinc plating of the metal components within the distributor. This is why we recommend venting the cap by drilling holes in the cap in some applications. This helps to vent the ionized air better.
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#12 03-13-2008, 07:14 PM
Ed White
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I live in Pennsylvania and I lived here with the Mallory distributor. The car is garage kept and driven only in the summer on nice days. The engine is an all aluminum 427 and it is vented at both valve covers and at the back of the intake. It does not have a pcv. I cut the side off the cap so that I could see what was going on. As you can see from this picture the new distributor shaft is already starting to rust after less than a year.
DistCutAway02s.jpg
I also noticed that the rotor is lower than the plug posts. I would have thought that it would be somewhere aligned with the side of the posts.
In the next picture you can clearly see that there is quite a big gap between the rotor and the post.
DistCutAway01.jpg


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#13 03-14-2008, 09:37 AM
TheMonkey
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Ed- i agree... that big gap seems kooky to me.

MSD responded that excessive secondary circuit resistance could result in the corrosion, and that gap seems like a huge resistance point ???

Perhaps crankcase ventilation is an entirely separate issue from your corroding distributor. Either way, I think you should reconsider not having a PCV valve. Research the benefits of a proper system. My feeling is that no PCV valve would be like not brushing my teeth. Yuck.

Just a couple quick notes you can take it for what it's worth....

Proper ventilation system will BOTH blow & suck through your breathers.

Right now, it sounds like you have plenty of ventilation so that at WOT, blow-by, and positive crankcase pressure will exit easily through your breathers rather than blowing oil seals or popping out the top of your oil dipstick. Without proper breather system the problems become obvious after WOT pull. You probably blow nicely, and see no problems.

But, you're not sucking. Not having a proper PCV sucking system creates problems that are quite a bit more surreptitious and cause longer term damage to the motor in the form of sludge and corrosive gases. At idle, a functioning PCV valve will use manifold vacuum to draw (suck) a controlled amount of air through the breathers, through the crankcase, through the PCV valve, and burn the condensation and acidic gases right out the tailpipes, instead of festering in the crankcase.

Your current setup is perfect to add a PCV. just convert your rear of the intake breather to a PCV valve and connect it to manifold vac on carb or throttle body. if you have another location to put a PCV valve, just make sure you draw the air through the crankcase; for instance... don't draw through PCV right next to breather, that's the only area your are circulating. Drawing from PCV valve in the valley through breathers at both rocker covers is ideal.

depending on how you spec the valve, it might require a SMALL adjustment. if you are fuel injected, just turn down the throttle stop mildly to set idle speed back to where it was. if you are carb'd it might require a tiny bit of richening at idle, but prob not enough to make a difference. i think my valve (on 462cid) draws 3cfm at idle, and 6cfm at WOT.

Consider this... for every gallon of gasoline burned, approximately 1 gallon of water vapor is created!

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#14 03-14-2008, 02:27 PM
Ed White
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TheMonkey,
Thanks for the pvc info, I have it on my to do list. I have a tunnel wedge dual quad manifold and have no place to put the other end of the pcv. I have all the stuff but I have been waiting untill the next time the intake comes off to drill a hole, the carbs do not have a port.
I think that MSD has a problem, the shaft is just basicly bare metal and does not seem to have any protection against rusting. The center button on the cap is another weak spot and many others are having a problem there also.
I agree with you that the very large rotor gap and the fact that it is below the poles will cause a lot of electrical discharge, big resistance and ozone.

I agree that I could benefit from a pvc but that is in no way related to the problems that I am having with this distributor. I drive this car to work on nice days and it is a good 45 minutes each way so it gets warmed up.

Thanks


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#15 03-15-2008, 05:20 PM
Rickman
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This is the issue:

http://www.msdignition.com/forum/showthread.php?t=11536


believe it!

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Last edited by Rickman : 03-17-2008 at 10:40 AM.


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#16 03-15-2008, 08:24 PM
dodgestang
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Quote:
Originally Posted by Rickman
This is the issue:

http://www.msdignition.com/forum/showthread.php?t=11525


Believe it.


Interesting post.

I have it back up and running. I measured the resistance and didn't see anything out of whack on my wires. My rotor when removed has 'some' black markings on it which I believe were prob from spark scatter/arching within the cap. I purchased a second setup and put it in the glove box...not the best solution but at least if I have the problem again I won't be stuck on the side of the road.


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#17 03-16-2008, 01:01 PM
Rickman
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MSD Says:
"There are a few reasons that could have caused the above failures. Excessive secondary resistance, poor contact with the rotor, cracked/damaged carbon ball (which could have occured during shipping or production for that matter) are just a few possibilities."


When only the "Red" caps were available I had discovered this and brought it to the MSD techs attention and got blown off. At that time I tossed the MSD cap and purchased a high quality one with brass terminals from NAPA. The application was for International Harvester V8, Napa # is AL 162. Another brand KEM #1553, also with brass terminals. Although I think the MSD cap is of better materials, the fact that the rotor (MSD#8467) is so far out of alignment concerns me. It needs to be addressed either by effectively redesigning and raising the rotor tip or perhaps shorten the cap overall or lengthen the contacts within the cap. OR explain wy it is this way. COME ON GUYS.................This dimension greatly increases the stress on the secondary ignition system.

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Last edited by Rickman : 03-16-2008 at 01:23 PM.


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#18 03-16-2008, 11:14 PM
Ed White
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Rickman,
Thank you, I agree. MSD how about an answer. Is the rotor supposed to be below the posts and so far away? Please look at the above pics, and let me know if this is correct or is something wrong.


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#19 03-17-2008, 10:03 AM
Rickman
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Ed White:

Refer to your second picture, and lower the rotor tip .160", creating a large gap between the rotor tip and the bottom of the tower post. That is my dilema on the #8579 distributor. Used for 302 Ford.

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Last edited by Rickman : 03-20-2008 at 12:01 AM.


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#20 03-17-2008, 05:05 PM
Ed White
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Rickman,
Lower the rotor tip? I would think that it needs to be raised. Am I correct in thinking that it should be aligned somewhere above the bottom of the cylinder posts? I would think that the rotor should fire straight out to the plug and not out and up.

Thanks for your replies,
Ed


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I hope this helps...

Your cap and rotor don't appear to be from the same manufacturer. I had trouble with the rotor hitting the cap when using an MSD rotor on another MFR's cap. I'd suspect excess gap between cap and rotor or a bad coil wire or plug wires. That would raise the firing voltage way up.
When I have run no vac advance the leading edge of the rotor was clean, like new. Yours looks worn all over like it's been run way too long. How long was in in the car?

Your cap and rotor don't appear to be from the same manufacturer. I had trouble with the rotor hitting the cap when using an MSD rotor on another MFR's cap. I'd suspect excess gap between cap and rotor or a bad coil wire or plug wires. That would raise the firing voltage way up.
When I have run no vac advance the leading edge of the rotor was clean, like new. Yours looks worn all over like it's been run way too long. How long was in in the car?



The cap and rotor are from the same manufacturer(Pertronix). The coil is not bad and the wires are brand new. The cap and rotor are from July 2007. Isn't the Crane ignition going to increase the firing voltage? Isn't that its purpose?