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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Pertronix Problem

I am installing a pertronix ignition system. I have all the correct items and everything fits EXCEPT the distributor cap. It will not sit down on the distributor body. Upon examination, I found that the distributor rotor is riding on the magnetic sleeve that covers the cam. The sleeve is held in place by a cover on top. It is the thickness of this cover that is not allowing the rotor to sit down on the top of the cam. I would ask anyone if they have had the same problem and how it was resolved. I tried installing it on another distributor but had the same result. Any ideas would be most welcome.
George Raham
TD4224
G. L. Raham

Hi George, I just ran into exactly the same thing. Glenn at Glenn's MG repair told me the Pertronix sleeve is a bit too tall to allow the rotor to seat all the way. You have to just file a little off of the base of the rotorto seat it, and all is well. George PS- we were up your way a couple summers ago- really beautiful!!
George Butz

George --- They must have changed something because mine fit like a glove right out of the box. Of course I'm negative ground and have the hi-lift cam in both cars.

cheers,

Bob
R. K. (Bob) Jeffers

Mine is positive ground. I installed it during restoration, and the distributor cap wouldn't seat- it rocked over the rotor (it is a NOS Lucas cap). George
George Butz

Hi Bob, Thanks for your comments on my problem. I am also negative ground with the hi-lift cam and the magnetic sleeve fits over the cam perfectly. Without the sleeve, the rotor sits right down on the top of the cam. When the sleeve is over the cam, the rotor is raised up the thickness of the sleeve top material. I am amazed that a product like this, is released on the market that requires the customer to modify a part to make it fit. In this case it is not a difficut modification and I will proceed as George has suggested.
Thank you George for your solution to my problem. When I dicovered what was happening under the dist. cap I figured that the only way, was to do what you suggested, but I didn't want to accept that as the only answer. I hoped that I had done something wrong but just could not understand what it might be. I'm glad you enjoyed your trip up our way. It would have been nice to meet you and have some "T" talk.
George Raham
TD 4224
G. L. Raham

George --- Why don't you call them and explain your problem and see what they say?
cheers,

Bob
R. K. (Bob) Jeffers

Some years ago I had the same problem, but I managed to b-----r up the sleeve. Phoned Pertronix and they sent me a new one which fitted on the first try. They seem to be good people to deal with. There was an explanation as to why the problem sometimes occurs, which I have now forgotten. In any event once installed it has worked perfectly and is a great improvement. Terry
Terry O'Brien

Likely part of the issue has to do with the distributor itself. There may likely be variation in the various cam heights as well as variation in the sleeve. Luckily easy fix. I wonder if anyone has measured a bunch of rotors to see if there are any height differences? Good thing the fix is easy. Certainly much cleaner installation than the old Crane unit with the separate box (which did work well however- even with the really cheesy pick-up mounting brakets). George
George Butz

Hi Bob, Thanks for your suggestion to call them. As it is Sunday now, I have E-mailed them so it will be interesting to see how they reply or if they do. Judging by Terrys experience (in the thread following yours) they will give what ever support they can. Fortunatly I am not in a desperate situation as my block is still in the machine shop.

Hi George, That was a good thought, and as I happen to have both a symmetric & a high lift cam I was able to compare and found no difference in the depth of the cams.

Hi Terry, I appreciate you comment and it encouraged me to E-mail them to see what they may suggest. Thanks for your interest.
George Raham
TD4224
G. L. Raham

George,
see http://www.ttalk.info/Tech/Pertronix_Into_TD.html The last line on the page says:
I've been told that it may be necessary to dig out a knife and carefully whittle out some of the material from the inside of the magnetic cap in order to get it to seat fully onto the distributor cam.

Marvin Grebow at Pertronix is the tech support person that I've had great success with. He's at 800-827-3758, email is marving@pertronix.com Bud
Bud Krueger

Hi Bud, I have established that the magnetic sleeve is sitting down on the shoulder of the cam without any interference. My problem seems to come from the thickness of cover on the sleeve that the rotor sits on. Thank you for the phone no. and E-mail address of Marvin Grebow. I have sent an E-mail to Pertronix for some advice. They have already acknowledged my E-mail and advised that I will hear from them in 48 hours. I hope they can come up with some solution. Thanks again for your input.
George Raham
TD4224
G. L. Raham

George,

Somehow, chipping, sawing, filing, etc. to get a part to fit, flies in the face of common sense. I feel Pertronix have an obligation to see this through.

Hope you will post your response from Pertronix. My unit fits perfectly (+ grnd), but perhaps we can all benefit from the info.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

Gordon C. You bet I will, as soon as I get a reply, and what advice they give me to solve my problem.
G. L. Raham

I have had several E-mails from Marvin Grebow at Pertronix in which he asked a series of questions about my installation. I was able to tell him what was happening with my distributor, and after talking it over with other people at Pertronix, they could not come up with an answer. Their only advice to solve the problem was to shorten the depth of the rotor. They also indicated that if this was not acceptable to me, they would assist in the return of the unit to the supplier. As I do wish to use the ignitor, I guess my only option is to file the rotor down so the cap can be clamped into place. I don't feel this should be necessary with a product that has been on the market for so long. I would like to understand why it is happening to my distributor. I told Marvin that I installed it on another distributor I have with the exact same results. I would like to know if anyone else has had this problem and if so, how they resolved it.
George Raham
TD 4224
G. L. Raham

George, you've really piqued my curiosity here. As I see it, there are only two components that are in the running for 'guilty party', the Pertronix sleeve, or your rotor. Iff I lived by you I'd ask you to give me the parts so that I could try them in my distributor to see what's up. However, I'm a long ways off. What is the number cast into the top of your magnet sleeve? See image for example:


Bud Krueger

George, You have to realize that this hobby requires a lot of fitting, fiddling, etc. Having been a serious T-series owner and hobbyist for years, I have had to fit, modify, and fuss with more parts than not. With limited, small volume production, things often require adjusting. I have spent countless hours fitting things from center crankshaft bearings, tach drive couplers, shimming reproduction generators, grinding water pump castings, and bending/tapping/fitting corner windshield pegs. Even things made to the original engineering drawings sometimes don't fit, due to running production changes. Again, this is a well known and common problem and the quick and easy solution is to file the rotor. The first electronic aftermarket ignitions worked well, took forever to install and adjust, required drilling and tapping the base plate, installing a really flimsy pick-up coil, running many wires to here and there, and you had to find somewhere to mount the control box, etc. Have to put it into perspective- it is just the nature of this hobby. George
George Butz

Good morning Bud, The number on my magnetic sleeve is not the same as yours. Mine reads LUI42 (no "A" like your image). Maybe that is my problem and they have sent the wrong part, how ever the sleeve fit very nicely over the cam. What model do you have yours installed in?
George Raham
TD 4224
G. L. Raham

George, The wrong one would also not fit! I'll check my number tonight if I can. George
George Butz

Hi George. The LU142A is from an image in 'my files'. It's probably left over from MGB days. I popped Lazarus' distributor cap and took the below image. As you can see, it's also an LU142 sleeve. I made a few measurements while I had it open. I measured the distance from the top surface of the distributor shaft to the top of the sleeve to be .314". I then measured the inside depth of the rotor and found it to be .367". That would say that the same rotor would sit .053" lower in the distributor with a point plate. Obviously, this is not a problem or Lazarus wouldn't be running. I then dug up a few more TD rotors and found some surprises. See my next post for another image.


Bud Krueger

Here is an image showing four TD rotors. The one on the far left is the type that I'm using in Lazarus. The one on the far right is a genuine Lucas. The inside depths range from .370" to .416" and the overall height ranges from .657" to .793". I can see where a rotor could be too high for the application. That thick one would most assuredly contact the underside of the cap.

George, can you tell me anything about the rotor that you're using?


Bud Krueger

Side view of three rotors. The Lucas one is virtually identical with the one on the right.


Bud Krueger

Bud,

Excellent photos...sure explains why problems might arise.

Gene
Gene Gillam

With the known problems we have with the latest repro caps, I wonder what part ,if any, they have here.

LaVerne
LaVerne

I had exactly the same problem last year when working on a Jaguar 120. The car would drive for four or five miles and then stop. Inspection revealed that the top of the rotor was pressing hard upon the distributor cap and wearing out the carbon bush. I tried different distributor caps but that did not fix the problem. The only cure was to grind about 3/32" off the base of the rotor. The car now has over 500 miles on it and is still running well.

I telephoned Pertronix and described the problem and they told me they had never had this problem reported to them before this incident. They expressed concern but, beyond that, were not helpful.

I wrote this up in this BBS about 8 months ago for others to note and you may find it in the archives somewhere.
G.E. Love

I pulled my cap to install bumblebee wire today. It looks like I have the same problem with my Pertronix. I ground the rotor down about .125" and reinstalled. I'll road test it in a couple of days.





Evan Ford - TD 27621

Hi Bud, Sorry for the delay in getting back to you regarding my rotor. It is identical to the one on the left in the top view of the 4 rotors. It even has the '4' on the brass contact, but mine is black. As best I can tell the dimensions match your rotor as well. The 3 black ones on the right would present a greater problem with the Pertronix Ignitor due to their greater dimensions. It looks like I will be cutting down my rotor to make it work.

Thanks to everybody for all your support and suggestions in my problem. I think it may let others know what they can run into if they are considering the Pertronix Ignition system.
George Raham
TD 4224
G. L. Raham

George & Bud,

Interesting thing with the rotor on the left. It has a counter weight molded into the base. It would appear to make contact with the coil on my pertronix. The coil on mine sits slightly higher than the magnetic ring. I also have a rotor like the one on the far right, which I currently have installed.

I might double check the counter weighted unit for contact. I would like to use it as a spare.
Evan Ford - TD 27621

Hi Evan, When I was comunicating with Marvin at Pertronix, he asked if the top of the ring was above or below the Ignitor. I told him that they were both flush. He didn't come back and say that was wrong, so I have assumed that they should be flush. In that case, there should be no interference between the rotor and the ignitor. Now where is that file.
George Raham
TD 4224
G. L. Raham

George,

I don't have any interference, the coil is just taller than the ring. Here's a cell phone picture, but the angle doesn't really show the difference well.

Evan


Evan Ford - TD 27621

Just received an e-mail message from Moss Motors which describes this "new" rotor:

New! 4 or 6 cylinder Premium Ignition Rotors

The carbon content in the plastic of most ignition rotors today is too high and the plastic becomes a conductor by design. More than just robbing your engine of precious spark energy, in some cases the spark can be misdirected to the spring clip on the underside and Presto! – no more spark. Don't let your ignition rotor ruin your Sunday drive, replace yours with one that is manufactured correctly.

151-805 $10.95 ROTOR, Ignition, Premium
4-cyl.

http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=67034&utm_source=British130&utm_medium=email&utm_campaign=Emailer

(The link above is long and may need to be pasted into your browser.)


Larry Shoer

Now we need a premium cap to go with it!!
Evan Ford - TD 27621

Just so you all know, those premium rotors from Moss are the same ones I sell for half that price!

I've also run into issues where the center post on the replacement caps is too long, contacting the rotor. You can remove the carbon brush, sand or file it down a bit, and put the brush back in to solve your clearance problems. Using an old original type rotor usually solves the Petronix interference problem though. Its pretty common in the TD distributors! They were made with a taller shaft assembly and less room for error than any other model. I think the guys at Lucas learned from their mistake and built distributors with more clearance post-TF design. The later DM series distributors all have a LOT more room for error!
Jeff Schlemmer

Jeff,

Do you offer a quality cap also?

Thanks, Evan
Evan Ford - TD 27621

Hello to all the above, This past weekend I removed 3/32" from the bottom of the rotor. Installed and timed the distributor. Got oil pressure,pulled out the choke, turned on the ignition, pulled the starter, and WHAM, it fired on the first rotation and I am very relieved. I would like to thank all those who offered their advice and suggestions in the above thread. It seems that no matter how long you have your car, you can always learn something more when you have the opportunity to access a forum like this one. Thanks one and all.
George Raham
TD 4224
G. L. Raham

This thread was discussed between 05/04/2008 and 06/05/2008

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.