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Benjamin A.R.

Burnt dizzy tabs...

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My search turned up nothing relating to this situation specifically. I was running a stock vacuum advance distributor with Crane XR700. I could never get the idle quite right so I swapped out the vacuum unit for a mechanical advance only one and kept the Crane as it was.

Since then I've been getting these char marks. I played with the optical trigger position and the char marks continued on a new cap. Is there a different trigger disc for the mech vs vac? I've only seen the one kind. Wires are new. I have a spare XR3000 module I could slap in, might that help? Different coil maybe?

As always I appreciate the help with electric stuff. I'm garbage at troubleshooting things that make the "bang" in suck squeeze bang blow.

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But good news since ya'll last heard from me: I replaced all the front tie rods and swaybar end links. The old ones were original haha. I stripped down the front hubs and replaced the bearings and races, pressed in New I.E. wheel studs so that the "new" BBS RA's in 15x7 with their 195/50/15 Falken rubber would safely bolt on. I installed H&Rs and HDs on all four corners. This thing does corners now! I added an I.E. heat shield and finally got the speedo working! I also fit the cherrywood console with the nautical compass that lights up GREEEN!!! Next time we moor up I have to do rear wheel bearings, studs so I can test fit the BBS's in the rear, CV boots, and drop the diff to reseal it. And yeah I'm still hunting for the Camden B80 blower, so I ain't slackin over here!

Happy New year

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To me, it looks like the rotor is 'running off' the end of the cap connections.

 

I had one that did that- the trigger wasn't aligned quite correctly inside the dizzy,

and it would have been a pain to move it.  So I used the VW rotor with the wide tip-

that solved it with minimal effort.

 

If I'm right about this, you'll see that one end of the rotor looks blackened, too, while the

other is shiny.  If there's no marks at either end, I'm wrong.

 

hth,

t

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Did I read somewhere that there is a distributor cap for a similar 4-cylinder bosch distributor that is slightly misaligned producing a 'rotor phasing' problem like this when fitted to an 02 distributor?

The typical fix for a phasing issue is to adjust the position of the pickup relative to the base plate to advance or retard as required as Toby suggests. MSD actually recommend drilling a hole in the cap and checking where the rotor fires with a timing light.

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I had that happen as well, when I had a Pertronix ignitor in my 002 distributor.

Apparently they do not make one that truly fits that distributor.

Rather than mess with relocating the ignitor, I went back to points... and a vacuum advance distributor.

(I missed having points to fiddle with).

Anyway, here is a photo of what tipped me off to the problem.

It looks similar to what you are seeing.

013.jpg

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(edited)

The relative position of the rotor electrode to the cap electrode changes all the time with the timing as the engine changes speed (mechanical advance) and vacuum advance (if the distr has one).  The total advance at any given time / 2 will be the degrees relative movement of the rotor to cap.  So there will be big spark jump within the cap at times where the rotor is a ways away from the cap electrode.  Burning of the cap / rotor electrode is unavoidable and normal.  If mis-aligned too far the spark will jump to the worng cylinder!

 

 

I need to correct myself.  Only the mechanical advance affects the rotor.  Vacuum advance moves the breaker plate, not the rotor, but under vacuum advance, the points open sooner, and so the spark jumps sooner.

Edited by jimk

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Right, Jim, but ideally the rotor tip's wide enough to cover the advance window.

So it runs on one side of the tip at minimal advance, and works its way to the other end when you get to

full advance.

 

And yes, I had that problem with a P-tronix when used as an MSD trigger.

 

Any VW shop can sell you the 'wide tip' rotor for a coupla bux- it is a band- aid, but it nicely covers the cut.

 

t

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I had that happen as well, when I had a Pertronix ignitor in my 002 distributor.  Apparently they do not make one that truly fits that distributor.

Rather than mess with relocating the ignitor, I went back to points... and a vacuum advance distributor.  (I missed having points to fiddle with).  Anyway, here is a photo of what tipped me off to the problem.  It looks similar to what you are seeing.

013.jpg

 

 

I am not sure I see a problem with this cap, other than the terminals could be cleaned of the carbon and the horizontal scribe marks should be avoided.  Yes, I too use the wide-tipped VW rotor, although I think mine was originally intended for a Volvo or Saab.   Look at the attached article on rotor phasing and it seems to suggest having the rotor closest to each terminal or at least toward the leading edge of each terminal when firing.

 

http://www.hotrodhotline.com/md/html/rotorphasing.php

 

 

Rotor_figure_3.jpg

 

 

No Vacum Advance:  The rotor tip should line up with the cap terminal or be on the leading edge of the terminal when the spark occurs. (Figure 3)  This ensures that the spark is jumping to the correct cylinder at the proper time.

 

 

 

rotor_figure_4.jpg

 

 

 

Things are taken to another level when holes are drilled in distributor caps as "ion vents"..   :blink:   https://books.google.com/books?id=h_aqxdCH2eUC&pg=PA98&lpg=PA98&dq=drilling+distributor+cap+to+allow+ions+out&source=bl&ots=bqAY1ivw02&sig=i3ex5LmkVCrWcZQtqTlDz6AaVh4&hl=en&sa=X&ved=0ahUKEwjhmtfX15jKAhUX_mMKHSn2BjMQ6AEIHTAA#v=onepage&q=drilling%20distributor%20cap%20to%20allow%20ions%20out&f=false     and   http://www.nastyz28.com/forum/archive/index.php/t-204273.html

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To me, it looks like the rotor is 'running off' the end of the cap connections.

 

Have you checked if there is excess vertical movement in distributor shaft by grabbing it and moving up and down? Is your timing mark stable when you pointing timing light to it?

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I've never been able to find the little ball that people say is set into the flywheel that serves as that mark. I'm not super concerned though because I have it pretty dialed in by ear and feel. And no the shaft has no more slop than the last one did.

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Paint that BB white.

It is worth the trouble.

I shot a spot of paint in the cap of a poof-can and dipped a bamboo skewer in that, to drip the paint on the ball.

It makes timing fun, instead of incredibly frustrating.

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That shaft will be on a roller coaster ride if shaft slop is more than 0.005" (0.127) and that is why IMO carbon is at the end of cap connections.

 

 

the shaft has no more slop than the last one did.

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