Pertonix misfit
 

Hello...

First let me say what a great resource this forum is. I just purchased a '72 280SE 4.5 and have found this a great place to get answers.

From what I've read here, I get the impression that my engine is under-performing. It just doesn't seem to be as powerful as has been described in various posts.

I understand that an under-powered engine could have many causes (leaky vacuum lines for instance), but thought that I'd start what with seemed to be the easiest - upgrade the ignition.

Tried to replace the points with a Pertronix Ignitor this past weekend and ran into a problem. The distributor cam is too "tall" to allow the magnetic ring that comes with the Ignitor kit to fit so that it is parallel with the "sensor" unit (sorry, don't know the name of the Pertronix piece that replaces the ponts). Also, the height of the distributor cam prevents the rotor from being seated all the way in. All of this leads me to believe that I don't have a stock distributor or somebody installed a non-stock cam on the stock distributor. I can't find a part number on the distributor, or any label for that matter.

Called Pertronix, they of course need a part number before they can do anything. Before I give up and uninstall the distributor and mail it to them, I am wondering if it is possible to simply install a new cam on the distributor shaft? Is that possible? If so, is it a relatively easy procedure?

Robert

Here's an install post with some pics. Give it a look and maybe you'll catch something installed upside down, etc.

http://www.mbzponton.org/valueadded/maintenance/ignitionpert/ignitionpert.htm

Assuming your distributor has not been changed, perhaps the magnetic ring is not completely seated on the shaft. A tap with a socket might be in order.

Did you grind off the corner of the mech advance arm as shown under the heading 'Minor Modification'? Could very well be your problem if you didn't.

Like the German license plate. I've got mine on my vehicle as well.

I did check out http://www.mbzponton.org/valueadded...gnitionpert.htm, which, judging by the pictures there, is making me think I have a non-stock distributor.

My problem is that the distributor cam is too tall. The shaft has only so much room, so that when I install the rotor there is only 1mm between the rotor and the cam. There is no room left to stack anything else on the shaft, so installing the magnetic ring is impossible. (wish i had a digital camera!)

It would seem that the easiest solution would to be to replace my cam with a shorter cam. That way, I would have enough space on the shaft to hold the ring and the rotor. I guess my only other option is to replace the entire distributor?

I'd grab the distributor model number (there's a little plate riveted to the side of the can ) and double check it with Pertronix Tech Support. There's quite a few models out there.

Joe.. thanks for your replies. Unfortunately, I can't find any part numbers or labels on the can. Guess I'm going to have to bring it in to the mechanic. :mad:

...could be missing, but should be there.

http://glenn-ring.com/hvw/107_0737.jpg

I would not give up on the Pertronix. I have used them for years with great results on many cars. But the problem you have encountered with your MB is similar to my experience with my 230/8. MB distributors seem to be many and varied, typically a collection of parts from the Bosch bins. There should be a small oval plate riveted to the side of your distributor. If it is missing, you may have a replacement of uncertain origin. That said, the Pertronix magnetic rotor is a tight fit on the cam. Look inside and you will see an octagonal recess that matches the shape of the cam. Align the flats and press down firmly. It will take strong pressure to seat the rotor, and once it slides down to the point of resistance, you are not done. Do not whack it with anything. Continue pressure until it bottoms out. The magnetic rotor must align with the stator pick-up, but must be neither too high nor too low. There is a "Goldilocks" fit, gotta be just right or it will not sense properly and the car will not run. It needs to sit just low enough that the distributor rotor can rotate without grinding against the cap. Try measuring the stock height of the OEM assembly from the point plate to the top of the stock rotor. This dimension will give you a guide to how far the magnetic rotor must slide down so that the stock rotor can clear the cap contacts without interference. The magnetic rotor should seat against the shoulder of the cam, but measuring will help you decide when to stop pressing on the magnetic rotor. Also, you need check the radial clearance between the magnetic rotor and stator and set to their specs.

If all else fails, sending it to the tech weenies at Pertronix will guarantee you a working set-up. They will make it work for you by mixing and matching from their own parts bin.

FYI, I finally retreated from using Pertronix on my 230/8. I use the old girl so little that changing the points was/is no chore; more like therapy in a stressful world.

Good luck to you. If you use your MB often, the Pertronix will be the best upgrade you ever make.

230/8

Joe.. thanks for the pic. I think my dist. housing might be of the aluminum flavor. From what I understand from reading some of the posts on this forum, the aluminum housings have the #'s stamped directly into the metal. However, I can't find find anything. Thanks for your help!

230/8... Because my dist. cam is so tall, I cannot get the ring to slide down far enough to align with the stator pick-up. The shoulder of the cam comes up to about half the distance of dist. housing. From the pics I've seen of stock distibutors, the cam is much shorter. I think my 280 is due for some down time while I ship the whole unit to Pertronix. Unless I can simply install a new, shorter cam?

Same issue
 

Hey Robert,

I just ran across this issue while doing my install. I have the original distributor 0 231 116 052 and the exact same problem. I thought perhaps the rotor was incorrect (having the guide tooth that connects to the shaft) too high.

I'm about to call Pertronix myself and see what's up, if I figure it out I'll let you know.

Burningman.. Cool, I would be very interested in what they have to say. Where did you find the part number for the distributor? Thanks!

if it's the stamped # version of dist. then it maybe hard to see since it is facing the block but if you look hard enough or use a mirror you should be able to find it...

Thanks mzsmbs. I finally figured that out yesterday and did locate the number. I'll speak with Pertronix today and post any findings.

By the way, my mechanic was very dubious about installing the Ingitor and Flamethrower. His basic position was that deviating from stock parts is often a path to a poor running engine (or worse). I can respect that.

However, the Pertronix gear is not simply a matter of replacing some moving parts (points) that are prone to deterioration. There is also the added benefit of a hotter spark and thus a smoother, more efficient running engine. Is that about right?

Lots of MB guys use the Pertronix/ Crane ignition modules. The points-based system can be fiddly and requires some upkeep. I found with the Pertronix unit that my engine smoothed out quite a bit and power delivery was more even. Hotter spark allows for a greater spark plug gap and improved the power my engine was producing.

I'd give it a try and if you don't care for it you can always switch back to the points.

even if you love it keep a spare set of points in your glove box.. just never know when you may need them and w/o spark you're not going anywhwere...