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MG TD TF 1500 - Pertronix igntition installation

Just thought I would share my experience in installing the pertronix in my TD. First problem started in selecting the correct unit. I looked at the illustrations in the service manual and compared those to my distributor cam but could not distinguish between asymmetric, high lift and whatever the other one was. I drove the car out to Skip Kelsey's, and we looked at it together and made an educated guess. Finally we decided on the asymmetric. When I got home and tried to slide the magnet over the distributor cam it wouldn't seat, so I assumed I had the wrong unit. I exchanged it for the other unit (there are only two for the TD) and found that fit was worse.

I talked to other members in the club who had installed these things. No one seemed to have experienced a tight fit over the cam. Finally with Skip's pen knife we whittled away at the plastic bridge inside the magnet on the first unit and got it to slide down over the cam. The car started right up. I had about a three mile drive home before I could set the timing.

I remember discussions long-ago about rattling in the gear shift lever being attributed to retarded timing, and I can attest that this was significant. Traveling uphill the gear shift lever sounded like marbles in a coffee can. I first tried to set the timing by the static method, but couldn't start the engine after three different tries. I finally resorted to a timing light, aligning the distributor to its original position, and then rotating it while the engine was running. I was surprised at how far off the timing was . . . actually advanced by about 80 degrees (360 degrees in the circle). With a timing light I set it to about five degrees advanced (rpm at 800)... rotating the distributor 30 or 40 degrees counter clockwise to do so. Now it runs like a dream. I used to think the engine was pretty smooth, but now it buzzes like a contented bee at all speeds. We just completed a 600 mile trip to Yosemite and back and it performed beautifully.

So, installation was not smooth and easy, and I have a suspicion that I have the magnet rotated a bit,on the cam, but the results are wonderful.

Andy Moyce
52 TD
Andy Moyce

I thought I was the only one who could not distinguish with any degree of certainty which distributor cam I have. I think the key to solving the problem is looking at the slot cut in the top of the shaft for the rotor. Its in a slightly different place for each one. I hope I'm right because I just ordered a Pertronix for my TD using that assumption as a crutch.
Jim Merz

There is an article by Chip Old reprinted in the NEMGT Register T Type Restoration Handbook with pictures of the three types of cams. Using that I came to the instant conclusion that I have a Symmetric one and ordered the Pertronix accordingly.Am expecting it momentarily and will soon find out if I have any ability to compare a rendition to reality. But from the picture the slot in the shaft for the Asymmetric and the High Lift appear to be in the same place and the differences between these two versions look as if they might be hard to spot.
Terry O'Brien

John Twist shows the cams on his site at http://www.universitymotorsltd.com

Go to the technical questions and I believe it is question 49. Its towards the last anyway.
Blake J.

Installed the Pertroix today. Symetric Cam and positive ground. Also had to slightly skim off the edge of the piece which fits over the cam in order to fit it.
The real problem though was with the instructions. The warranty sheet says that the Ignitor is to be used only for negative ground systems and has three diagrams. None of them are applicable to the positive ground installation. The instuction sheet does in fact deal with the installation for the positive ground system except that the warranty sheet and its three diagrams are very misleading. Pertronix need to attach another diagram for the positive ground installation and tell you to ignore the three diagrams attached to the warranty sheet. Or they sent the wrong warranty sheet.

In the end however it seems to be a very significant improvement.
Terry O'Brien

First of all, hi to Jim Mertz. Haven't spoken to you in a bit. Do you have the Td MK 2????

2nd. I love the Pertronox unit. Put it in my TD about 6 months ago and the car has perfromed flawlesly. Last week was out in brutal hot weather and never had a problem. Previously, the car would not like the heat and balk or would not re-start. In the beginning, I had a slight problem with the rotor, but all is well.
Also found the instructions great so maybe Pertronix sent Terry OB the wrong sheet.
Cheers
Tim Gladding

My installation instructions with the unit were for positive ground also. So as Tim said they must have included the wrong instructions. The two wires on the unit go to the ignition and to the coil (- term or
ign) then from the coil (+ or CB) to ground. The hall effect switch is between the coil and the input ignition hot lead, rather than the points switch between coil and ground. Observe the polarity of the two wires to the unit ( I don't remember offhand which
goes to the coil ( black or black with stripe)
Don Harmer

I'm still having some minor timing problems with the pertronix. I haven't been able to static time, using either light off or light on as an end point, so have to resort to timing light. The problem, I've been told, is that above 6 or 700 rpm the spring weights come into play, so the setting will be a little retarded.
I currently have it set (idling at about 800) at a few minutes before 11 o'clock . . . assuming TDC is 12 o'clock. Runs okay, but I'm getting gear lever rattle on acceleration. The rattle wasn't there when I had the timing set closer to 11:15 or 11:30. Should I go back there?

Andy Moyce
52 TD
Andy Moyce

Just reading along here enjoying my wifes out of town trip.So, what the heck is Pertronix, do I need one and where do I get one if I do, and (and) do/does it work on mgtf. Dave Cates.(Trainee).
David Cates

Andy, since the centrifugal weights are adding a little advance at 800 RPM, I set mine at about the 1230 position. This gives me a little advance plus whatever I get from the weights which should take advantage of today's better fuels compared to those of the 1950s. Mine runs like a top and starts readily.
As for the static timing, I THINK that might not be possible becase it was based on the points opening. With the Hall Effect ignition (Pertronix), it doesnt work the same way without some amount of motion. I'm not positive about that I must admit.
Jim Merz

Am I confused, or isn't 12:30 postion a little retarded? (to the right of TDC). I've wondered if I couldn't just get a protractor from a stationary store, and mark 32 degrees to the RIGHT of the TDC mark on the pulley, then have my lovely assistant keep the rpm at 3000 while I set the new mark to the pointer using the timing light.

Andy Moyce
Andy Moyce

Jim,
You can static time with the Hall effect device since it depends on the strength of the magnetic field, Not the change in magnetic field. I set mine with the timing mark at 1/4 inch before the pointer (5° before TDC, counter clockwise) for my TF which has the later Hi-Lift cam distributor. This gives the correct advance at 3000RPM as seen by the timing light for today's fuels. One may have to jigger this for best running. But it should ADVANCE not retard the timing.
After setting static, check with a timing light to be sure the mechanical advance is working properly over the range and full advance is correct for your distriutor.
To get the correct distance, measure the diameter of the pully, the circumference is pi x d, and the distance needed is ( degrees advance/360) x pi x d.
Don Harmer

As you face the front of the engine, the crankshaft pulley rotates from your left to your right or clockwise. Consider the timing mark on the pulley as being 12 o'clock. As the timing mark and the pointer are lined up and the ignition fires, its firing on TDC (except for any advance provided by the extension of the centrifugal weights which we won't consider for this example). So if it fires before the timing mark comes to the pointer, (12:30), it has some undefined amount of advance set in in the timing. It would be retarded if the engine fired after the timing mark rotated past the pointer.
Jim Merz

Jim
I think I see where we are getting confused. I am considering the pointer as the fixed point and that point as 12 o'clock. If it's firing before it gets to the timing pointer it's firing at 11:30, and therefore advanced . . .yah?
Andy
Andy Moyce

Andy, I agree that we are talking about the same thing but from different perspectives. I also tinker with the timing setting to see what will provide the best performance from the engine. So far, I'm happy with the way it runs now which is some degree of advance other than TDC.
Jim Merz

This thread was discussed between 31/05/2000 and 28/06/2000

MG TD TF 1500 index

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