Distributor Rotor & Cap Rapid Erosion

[type26owner]

Made a change recently to my ignition system by going to copper spark plug wires and as a result might have upset the delicate balance. Have noticed the oxidation process that erodes away the electrical terminals surfaces by the sparking jumping across the air gap has increased to the point the cap and rotor are burnt to a crisp in less than 10k miles. It had not failed yet but from the looks of it but it would not have been very long before that was the inevitable outcome. There is a grey sheet of presumably aluminum oxide now coating the inside surface of the cap because of the cheap aluminum terminals. Aluminum oxide is comonly used as a lapping compound and as an abrasive will quickly destroy things like the plastic rubbing block on the points, advance mechanism fits and the plastic thrust bearing at the top of the mainshaft. Luckily it's not conductive though. Aluminum is just about the worst metal to expose to ozone also and because these dizzies are not vented they were never intended to have aluminum terminals fitted. Looks like maybe three corrective actions are necessary to get it to back up to best practice standards. One, to start using resistance type spark plugs. Two, modify the dizzy by adding a forced air venting solution to flush out the ozone. Three, modify the crappy cap by cutting back the aluminum terminals and in place installing copper or brass ones. This looks to be not all that hard to do actually. With oxidation resistant terminals in place they should last for 100k miles like the original Lucas cap did. What makes this true is the fact that copper oxide is almost as good an electrical conductor as the pure metal.

Ignition system other components consist of a Pertronix Ignitor, 27kv 3ohm coil and a noise suppressor.

Anyone else notice this effect? Pleased I found this problem on my Elan first because a similiar ignition system with an aluminum terminal cap is now on our race car. IIRC, it's coil is a 40kv variety and there is a CD module to get full coil saturation above 8k rpms. That is not going to hold up for even close to 10k miles!
-Keith

[type26owner]

Oh, forgot to include I have not checked the size of the air gap between the rotor and cap combination yet. Perhaps they are mismatched and the gap is excessive. Along those lines I'll check the angular phasing of the plastic magnet carrier for the hall effect switch relative to the rotor and cap position. This could lead to a larger then desirable air gap at either the low or high rpm range.

Anyone tried electroplating the aluminum terminals with a flash of nickel then a thicker coating of copper or gold before? A couple of thou copper plating buildup might be the trick solution to the oxidation problem. The cleaner and small plating kits totals about $70 from Caswell.
<a href='http://www.caswellplating.com/kits/index.html' target='_blank'>http://www.caswellplating.com/kits/index.html</a>
-Keith

[tdafforn]

Alternatively you could always flush the cap with a stream of nitrogen, or argon

[type26owner]

Here's a possible solution. Glued in place with silver conductive epoxy. The only issue is whether it's a good one idea or not. Estimated maximum operating temperature is right around the maximum rating for this type of epoxy which is -76 to +257F.
<a href='http://www.mr2sc.com/websites/Products/DistCap.html' target='_blank'>http://www.mr2sc.com/websites/Products/DistCap.html</a>

Actually Tim I've been pondering the issues of evacuating the dizzy. Unfortunately it exerts an axial force in the wrong direction away from the plastic thrust bearing.
-Keith

[type26owner]

Tim,
With the way the rotor and cap are arcing now maybe I need to affix tiny trefoil radiation warning labels onto the cap and warn everyone not to linger in the area. :rolleyes:
-Keith

[type26owner]

Measured the air gap at .028". That value seems to be within the acceptable range. That does leave enough room to allow copper .010" thick pads to be glued onto the aluminum terminals and most likely not foul the rotor. Primarily going through this process so I can start using the famous Lucas 'Bumble Bee' spark plug wires again. I really like the look of them fitted onto the twincam.

Next hurdle is to wind up the advance springs that are now unobtainium. Ordered various diameters of full hard spring music wire and a cheap hand held lathe tool for winding up springs. I've wound many springs before using this type tool and know how it's done. Why none of the commercial extension springs will work is they all have quite high intial tension force values. The ones for the advance need to have that set nearer to zero.
-Keith

[BillGavin]

Keith -

I got a few sets of mechanical advance springs from Don Tingle - I think he still has some in stock. I'm told that the springs are the same as some from an American distributor, but have never found out which one.

I'm using a standard Lucas cap and rotor with a Pertronix Ignitor and standard Lucas coil in my S2. I've been using the Bumblebee wires for four years with no problems at all.

- Bill

[type26owner]

Hi Bill,
Thanks, I'll call Don and have a chat. Are you commuting with your car like I am? I rack up at least 12k miles per year. Running duration is the key to this eroding effect being a much larger and quicker happening problem. Suspect the oxidation process is accelerated when the cap has fully heat soaked and the arcing across the airgap has taken place long enough to highly concentrate the amount of ozone. If you're primarily only making short trips then this corrosion process will happen at a slower rate. Hot aluminum turns out to be almost the best getter (most reactive metal) for ozone. BTW, when the plastic cap heats up it also expands some which opens up the airgap even more.

If you've got a vendor resource for Lucas DC1 dizzy caps I'd be most pleased if you'd share that info with me. All the Lotus parts houses I've called so far are only carrying the ones made by Commercial Ignition with aluminum terminals. Probably going to contact the CI folks and plead for them to build us a quality cap again. Worst thing they can tell me is no.

I'll try and take some photos of the cap and rotor and post them in my briefcase folders. Now that I think about it I should send them to CI also.

-Keith

[BillGavin]

I drive the car quite a bit, but here in New England we have a bit less Lotus weather than you have The car has accumulated about 11K miles since I put it into service in July 2001. I've paid next to no attention to the distributor in that time. I'm running N9YCs at .030" gap.

I haven't looked at the cap in a long time, but I think it's genuine Lotus: it would have come from one of the usual suspects - DB, RD, or TLC. I don't especially like the caps with aluminum contacts, but I've had serious problems only with the ones that have very small diameter contacts. Rotors have been a mixed bag, most last OK, some fail after a short while, usually by leaking through the plastic, sometimes with the contact bar faling out. Points are another story, I have a set of aftermarket points with maybe 100 miles on them, that can't be adjusted to .015" gap.

My usual solution to failures is my box of old caps and rotors accumulated over the years. The old stuff works pretty well

[type26owner]

Bill,
Ordered at set of advance springs from Don but both he and I have our doubts they will replicate the original advance curve since both springs are the same size wire diameter and wound the same way. Don also claims he can get dizzy caps with brass contacts. That would be terrific!. Found a MG parts source yesterday that also said there was a German supplier of the DC1 side entry dizzy caps with brass contacts. Ordered a couple of caps from both vendors. Thanks for pointing me Don's way.

Yup, the drophead was tailor-made for California's weather. Now get out of the way!
-Keith

[BillGavin]

I used to put two light springs in the distributors for my racing Sprites and Minis. The initial advance was delayed a bit, but it all came in by the time the engine got into its power range - we mostly wanted the timing retarded for starting.

I haven't plotted out the curve for the Elan distributor - two equal springs without an extended loop on one can't produce a knee in the curve, but if the curve is a straight line it may be OK.

I built up a distributor from an old Cooper S unit and a pair of Don's springs to try in my S2. I have a bit of pinging in my engine at wide throttle/low revs, so I'm hoping I can delay the advance a bit to make it easier to drive around town. I'll run it on a distributor machine before I put it into the engine.

[type26owner]

Bill,
Had my faith in Lotus engineering tested to the breaking point with the discovery of the the debacle they made of the Weber tuning. So with that bias I now ponder whether the advance curve is a best one for the stock configuration engine. So yeah maybe a straight line slope for the advance would be better. If I'm ever to make that determination I'll post the result here.
-Keith

[stelz]

Regarding all this Dissy talk, I was wondering if anyone has thought about use a programable advance unit such as

<a href='http://www.delta-digital.com.au/Deltamax%20Info.htm' target='_blank'>http://www.delta-digital.com.au/Deltamax%20Info.htm</a>

This thing seems cheap for what it does, not more spark scatter. Only down side is you still need to use the dissy for the HV distribution to the spark plugs.

Any thought on this one ?

Ben

[steveww]

A better solution is <a href='http://picasso.org/mjlj/index.jsp' target='_blank'>http://picasso.org/mjlj/index.jsp</a>

I have been considering this but I like the fact there are not any computers on the Elan and I would like to keep it that way.

[stelz]

I must agree that the MegaJolt looks good. Only problem is that you need an EDIS4 unit and I don't think they are available in Australia. I have been considering going all out and using a factory Nissan CA18DE ECU which can be fairly easily remapped (software is available on the web). This then gives a distributorless direct fire ignition which can be dyno mapped to match requirement. A bit of work in it though as the cam angle sensor would need to be mounted where the distributor goes.

Anyway, I thought the Deltamax went a long way towards a very reliable spark for only $330 Aussie $.

Ben