MSD Rotor Modification

[brads911sc]

Installed the MSD 6 AL in my 83 SC.

I have read at least 20 post about a modification to the ignition rotor, yet I cant find the modification described in any detail.

Can anyone point me in the right direction?

Thanks
Brad

[dailyATX82sc]

rotor??? i think a fresh bosch cap and rotor are ok. i would do wires and at least a "blue" coil...... also plugs gaped a tad bigger

[moneymanager]

Think this is misinformation; there is no rotor modification I know of, and I can't imagine why there would need to be. Just use the MSD with the stock rotor and cap. Maybe someone was talking about eliminating the rev limiter on the rotor, a step neither necessary nor desirable with the MSD?

[RoninLB]

i eliminated the rpm limit rotors to the simple Bosch rotor.

Pelicanheads have reported problems with the mechanism's connectiors causing them to toast.

some interesting pics were posted of the damage
yes.. some posted that same could happen on using the Bosch CD. For some reason all toasted pics were from guys using MSD.

personally same crap as with an old Beru plug connector. If you open one up there will be a few weak areas in waiting. For some reason the MSD toasts these weak connections on an aged Beru.

my attitude with electric circuits is to keep it as simple as possible for reliablity

[jpnovak]

the rotor mod is easy but not always necessary. If you look at the top section of the stock rotor you will see an area covered (potted) in epoxy. There is a resistor inside the epoxy that may not hold up to the extra voltage supplied by the MSD. If you run a larger gap, and thus a higher output voltage to make the spark jump the gap the resistor can quickly be overload. This means it will disintegrate and you have very poor performance. The epoxy section will sometimes be bubbled or even discolored depending on the amount of heat the resistor took in. the resistor is for RF noise abatement and not needed.

the solution is to take a dremel tool and mill away the epoxy. yes, you will likely zip right through the cooked resistor. Not a problem. Keep cleaning the epoxy our until you find the center brass contact and the outer brass contact. There you will find some solder where the resistor leads have been attached. Simply unsolder the resistor leads and bridge both contacts with a small section of brass or Cu or similarly good conductor. Test continuity with a Multimeter before filling it with epoxy. problem solved.

btw, the orange bakelite material is quite a bit harder than the epoxy giving you a built-in stop for the dremel milling step. Go slow, its easy to cut. Sometimes you can mill around the perimeter and pop out the epoxy slug depending on how bad the resistor blew up.

[brads911sc]

Thanks Jaime. That is exactly what I was looking for. I have gapped to .045 and switched from the Stock Beru Braided to Magnecor Wires our host sells. I also switched to the Blaster Vibration coil from MSD. Ill try to run it without the mod and see what happens. I bought an extra rotor just in case. Thanks all for your input...

[RoninLB]

this is what I use

Bosch box # bos-04038

Pelican # 930-602-902-00-M14 @ $6.25

http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=930-602-902-00-M14&catalog_description=Ignition%20Rotor%20%2D%20Bosch %2C%20%39%31%31SC%20%28%31%39%37%38%2D%38%33%29%2C %20%39%31%31%20Turbo%20%28%31%39%38%36%2D%38%39%29

[moneymanager]

Who would have thought? Have never heard of this.

[brads911sc]

Thanks Ronin . Thats the rotor I bought so I may be fine with no mods. Thanks, Brad

[RoninLB]

no problem all

just when my 911 is out traveling around the US I'm coming by looking for coffee

[jpnovak]

FYI there is a VW rotor that does not have the resistor. John Walker posted the part number long ago but I could not find it in a search. I think there is an early car and SC size (Shaft diameters are different).

[brads911sc]

Thanks Jaime. Ill drop John Walker a note.

[RoninLB]

Originally Posted by jpnovak

FYI there is a VW rotor that does not have the resistor. John Walker posted the part number long ago but I could not find it in a search. I think there is an early car and SC size (Shaft diameters are different).

Rotor button melting!! Why?

Originally Posted by john walker's workshop

vw bug rotor fits 72-77 for sure, but if i remember right, there's a shaft size issue on the earlier ones, and the rotor will wobble.

[RWebb]

very interesting -- does this apply to the 964 twin distributor rotors also?

[jpnovak]

Randy,

I do not know if the 964 rotor has a resistor. put a MM between the center contact and the edge. It should read near 0 ohms. If higher than a few Ohms (contact resistance) there might be a resistor in there. Keep an eye out if running anything more than a stock ignition. IIRC, you are running single MSD with twin coils.

FYI, I am running Crane Hi6 boxes on my car. I have blown two rotors in 6 years. Once they are "fixed" with a jumper, they are trouble free.

[aricaandjustin]

Found the link- thanks for the help...I will start on it tonight

[RWebb]

thx, yes - single MSD with twin coils...