MSD rotor burn problem

bplante · 12-22-2004, 07:21 PM

I have 1974 911. Just installed MSD 6Al with Blaster 2. Also am using new shielded Beru wires (not copper due to relatively high impedendence). Hard to start sometimes but it runs awesome. Keep burning up rotors. Have not used a Bosch rotor yet. How to solve this?

Lorenfb · 12-22-2004, 08:32 PM

That's the problem with having too much spark voltage/energy. The original Bosch
CDI provided adequate spark voltage & energy. Aslo, having multiple sparks causes
the life of the cap & rotor to be reduced by N (number of sparks per cylinder fire
where N is 1 to 6 below 3000 RPMs for the MSD).

Check out this web site (www.systemsc.com) on the Technical page for more info.

al lkosmal · 12-22-2004, 09:07 PM

MSD w/blaster coil for the last year or so. Lots of miles w/no problems at all.

RoninLB · 12-22-2004, 11:25 PM

an old rev limiting rotor may be a prob w/ MSD? I don't like it when it's new w/MSD.

fwiw, I wouldn't be suprised if MSD eventually wears on the Beru connectors?

Howard M · 12-23-2004, 08:35 AM

I don't know why the MSD (or any CD system) would supply any more voltage than the minimum needed to jump the biggest gap, regardless of the maximum capability of the box. Check plug gap (don't go crazy big) and rotor-to-cap gaps. My MSD and Blaster have given me no rotor problems (also installed Pertronix to eliminate points).

Howard

Early_S_Man · 12-23-2004, 08:45 AM

I haven't done this, since I don't use or advocate MSD ...

But, one possible solution would be to take a new Bosch rev-limiting rotor ... and 'bridge' the Glyptal-covered resistor element with a row of 5 or 6 parallel 30 gauge wires soldered to the brass ends where the resistor element terminates. Brass stock could also be used. The power rating of that resistor element is apparently too low for use with MSD, and I don't think soldering a higher-power rated resistor to the rotor would be a good idea!!!

jhora · 12-23-2004, 12:54 PM

I had this problem with a Crane HI-6 and Crane LX-91 coil. This was used with a Bosch 050 distributor, Pertronix Ingnitor, all in a 914 Type 4 engine.
It kept burning up the rotor's resistor and causing arcing inside of the distributor cap. Tried the solid copperwire to replace the resistor in the rotor. Still had the arcing. Finally went to a MSD distributor which hada larger Ford type Cap and solid core rotor...no problems then.
It seems that in my case the spark was just too hot for the rotor resistor and the Bosch cap spacing to close for the increased spark also.

Lorenfb · 12-23-2004, 01:10 PM

"I don't know why the MSD (or any CD system) would supply any more voltage than the minimum needed to jump the biggest gap,"

Ask MSD that question. That's their big selling point. Many get "sucked" into that B.S. hype.

Do a search, many have reported this problem.

H20911 · 12-23-2004, 01:15 PM

with a GM car had the same problem with the hi 6 and MSD because the pin from the center of the rotor needs to lower resistance than a stock one.

if the rotor has a resistor then do as Warren said and bridge it or use a solid rotor and that will solve your problem.

randywebb · 12-23-2004, 02:20 PM

Warren - what is your preference for a CDI unit?

911pcars · 12-23-2004, 04:55 PM

If it's a rev-limiting rotor, I think there's a solid (no resistor), VW-Bosch rotor that can substitute. One shouldn't need a rev-limit rotor with an MSD which uses chips to limit engine-fired rpm.

Sherwood

fred cook · fred cook's Garage

I have had an MSD 6A and Magnacor wires on my SC for over a year now. No problems with the cap rotor, wires, plugs or anything else associated with the ignition system. Of course, the SC distributor does not use the rev limiter rotor so any problems with the rotor resistor is eliminated. I certainly don't feel that I was "sucked in" by any MSD advertising! The ones that are getting "sucked in" are the Pcar owners that shell out $400 or more for a reconditioned Bosch CDI!

Fred Cook
'80 911SC coupe

Lorenfb · 12-23-2004, 05:21 PM

"The ones that are getting "sucked in" are the Pcar owners that shell out $400 or more for a reconditioned Bosch CDI!"

That's why Bosch and OEM car manufacturers laugh at the MSD technology and
at those that believe in the hype. If the technology had ANY merit, Bosch and/or
the OEMs would utilize it. There's nothing complex/unique about the design.

It's kinda like the "turbo" unit they sell to insert in the fuel line for better mileage
and performance. There's always someone who will believe the hype!

911pcars · 12-23-2004, 05:26 PM

"That's why Bosch and OEM car manufacturers laugh at the MSD technology and at those that believe in the hype."

Loren,
Just curious. What part of their spiel do you consider "the hype"?

Thanks,
Sherwood

fred cook · fred cook's Garage

Hmmm, $400 for a rebuilt Bosch CDI or $150-200 for a new aftermarket unit that works just as well (maybe better, but we won't go there)! The extra $200-250 bucks might be worth it to the purists that insist on keeping their cars absolutely stock but is hard to justify for anyone else! I guess ole P.T. Barnum was right....There is one born every minute!

Fred Cook
'80 911SC coupe

EWPurdy · 12-23-2004, 05:48 PM

MSD Digital 6+
High Vibration Coil
Magnecore Wires

3+ Years with no problems

To quote Steve at Rennsport System's Web site:

....replacing the stock CD amplifier and coil with a High-Voltage, High-Current unit such as the MSD-6AL or Crane Hi-6 and their respective matching coils. These units provide a FAR hotter spark that is better able to fire the rich idle mixtures required by Weber carburetors and MFI as well as firing the wide plug gaps that have been proven necessary for best power. These ignition boxes can make a race-cammed Webered’ high-compression engine idle for hours without any signs of distress when installed properly. The multi-spark high current ignitions really help reduce the cantankerous nature of some carbureted and injected engines that have mixture troubles caused by big venturies and high-overlap cams. These ignitions also feature some nice adjustable soft-touch rev limiting.

It's your money. I paid several hundred less for the MSD and never looked back.

Lorenfb · 12-23-2004, 07:32 PM

"These units provide a FAR hotter spark"

That's the problem, and that's why ignition parts burn! Well said.

Bottomline:

If a Bosch unit had been used, then this thread would not exit!

911pcars · 12-23-2004, 10:13 PM

"These units provide a FAR hotter spark""

Yeah, marketing hype, but apparently the multiple spark units help idle and low speed running on early Weber and MFI engines. Not sure there's a demonstrable difference in a CIS engine other than replacement cost.

Sherwood

bplante · 12-23-2004, 10:50 PM

This comment is not relevant to solving the problem.

911pcars · 12-23-2004, 10:59 PM

BPlante,
Just b.g. info that goes with every thread discussing MSD, Crane and Bosch issues.

Back on the subject at hand. You first stated:
"Keep burning up rotors. Have not used a Bosch rotor yet. How to solve this?"

Whose rotor are you currently using?

Sherwood