Running Rough: Dizzy questions (pics)

[NC Rover]

It also looks like there's more spark voltage than that cap is designed to handle. Are you using a Pertronix high output coil? Could be it's too much for the stock cap to handle. Just a couple of thoughts. HTH

This could be a possibility as well. I currently have a Jacobs Ignition with a Super Coil and Petronix Ignitor (no points).

However I've run this setup for about 3 years now with no problems.

If there was in fact too much voltage for the cap to handle, what would you recommend I do to balance it out? Are there aftermarket heavy duty caps made specifically for that kind of voltage?

[NC Rover]

Your problem may, as often happens, be a combination of things. Reading your description of the aftermarket ignition system you have and the condition of that dist. cap, would make me wonder if you have a compatibility issue. What is the resistance of the Super Coil you are using?

Thats a good question as it was installed by the previous owner who probably had the same setup for several years before I bought it off of him.

My engine is the 2.5L w/ a Turner Engineering head (oversized valves/higher lift cam, etc). Not sure if this would have anything to do with the choice of Ignition setup.

Both the Weber DTML 34/36 Carb and Lucas Dizzy are about 5 months old so they are pretty much new.

How can you determine how much voltage is coming from that Super Coil?

[kevkon]

It's not the voltage, it's the resistance and amps that are an issue with the Pertronix Ignitor ( which I assumed is what you have). Go to their site http://www.pertronix.com/support/default.aspx if you don't have a manual. You can measure the resitance of your coil or look up it's specs.

[bkreutz]

There's probably a machine to test coil output, but that's kinda out of the realm of owners, only option would be to ask the original manufacturers. I don't think there are HD caps made for a Rover (not enough of a market I suspect) But all the high power coil/ignition manufacturers make a HD cap for the normal hot rod stuff (Ford, Chevy, Dodge).

[cgalpin]

I believe you are right. If the arm is spinning counter-clockwise, then those burn marks are occurring right before the arm gets to the metal contact point.

So that would mean I need to rotate the dizzy clockwise just a hair. Does this sound correct?

Yes, but make marks to keep track of what it was before messing with it. I haven't adjusted the timing on a series yet so can't offer any other advice.

[Apis Mellifera]

stomper: MSD stands for multiple spark discharge. It doesn't increase the spark amperage, it just sparks rapid fire rather than a single discharge. It makes for a more complete burn.

In my MGA, I ran a Lucas Sports coil, an MSD 6AL, and stock points when I was racing it. It ran well, but the points did not last as long. I think your components are fine. You must just have a lot of hours on that cap.

The rotor just brushes the terminals in the cap. This produces some arching and resistance. Over time, the arching creates the deposits you are seeing. The deposits create more resistance, which creates more arching, which creates more deposits... The reduction in performance is gradual and isn't noticed until a misfire develops. The misfire causes the plugs to foul and it's a downward spiral from there.

Your plugs look sooty to me rather than wet with gas. That suggests a weak spark and/or a carb running rich.

I think the biggest mistake people make with British machinery (and what rarely produces satisfactory results) is to attempt to tune around faulty parts. I've been fooling with these things for over a quarter century. I've been hearing how unreliable British cars are, how poor the electronics are, and how difficult they are to keep running. To me that says more about the mechanic than the machine.

Bit of a tangent there and I'm not suggesting that applies to you, NC. My point is ALWAYS replace worn or faulty components FIRST. THEN you make tuning adjustments. In this case, I'd replace the plugs, rotor, cap, and probably the wires too. Next, I'd check/adjust the timing. Finally, I'd check/adjust the carb.

If it ran well before and then didn't, the timing and carb didn't just unadjust themselves.

Good luck.

[kevkon]

I agree Apis, you are dead on.
NC Rover, the arcing is not remedied by turning the distributor. As Apis said it's common and sometimes exaggerated by ionization in the cap or a faulty ignition component. Occasionally we would see this as a result of too much spark plug electrode gap in higher compression motors. In a sense the current seeks the path of least resistance.