Rotors hitting inside of cap

[Brosky]

Well, as Dale and Bill always say, it never ends.

Finally done with linkage issues on tr-carb setup. I decide to check out very slight skip on acceleration under load. Timing, carbs all usual suspects set correctly.

Oh, I also notice that my timing mark seems to to be jumping back and forth about 1/2" at idle for no apparent reason. Jeff from Advanced had said to add a few drops of oil under the rotor every season and to hit the advance springs as well with a drop or two, so I thought that I would do so and call it a night.

So I pull off the cap and reach for the rotor, which is #3, from the left in the picture. But first, being an old timer, I decide to just see if the rivet is loose. New rotor, but check it anyhow. Guess what, it is loose!

Great I say, I head to the trunk and open up my emergency bag of parts and pull out the spare three rotors that I have. I notice that they are different, but I figure, what the heck, just a newer design and must be the same.

So, I start the car and what a noise and racket as the engine sputters like crazy. I shut it down and pull the cap and tiny metal shavings everywhere! All three hit the inside of the cap. What the heck is up with that? When you start the car, you can see the cap moving as the rotor turns round and round. And yes, they bottomed out down on the Pertronix round ring.

Anyone have a picture of their rotors, as mine are all the same? I was going to swap out the distributor tomorrow and put the new adjustable one that I had Jeff build for me in, but I want to know why this is like this before I put it in as a spare.

Anyone ever see this? It's new to me. /bcforum/images/%%GRAEMLIN_URL%%/pukeface.gif

 

[RonMacPherson]

When you buy a new cap, make sure you get the same brand rotor to fit it. Bosch and Bosch, Lucas and Lucas, Blue Streak and Blue Streak, etc.....

 

[Brosky]

Maybe that's why the caps and rotors don't hit on all of my spare distributors. Jeff matched them up when he put them together.

But you should be able to buy a replacement rotor that will fit without having to change the cap.

 

[Guest]

As he said, never mix brands. I carry two caps and 6 rotors when leave home for anything more than an hour away......

Also, not all dizzy rebuilds are the same. When I lube mine, I take it apart to check everything - and I mean apart. Really need to get a spare; had one, sold it. dumb

 

[PlaidMan]

I had that problem once, all that was needed was to file or sand away some of the material at the bottom of the rotor, till it seated completely. You can figure on taking off about the thickness of the top of the pertronix unit. That thickness,in my case, was enough to cause inteference with a new rotor I had purchased.

 

[LastDeadLast]

Now you know why I installed the Mallory... The Pertronix is a nice unit, however the dizzy is crap for any type of performance applications (or any application IMO). PLUS, I didn't sink tons of $$$ into my heap to worry about the rotor self destructing.

I know I'll start a flame war for what I just said, but I went through 3 dizzies and 4 rotors before I trashed it. My little Mallory hasn't missed a beat from day one.

 

[tomshobby]

Interesting, I have mentioned having this problem several times in different threads and nobody ever responded that they encountered it.

I also notice on Paul's rotor the third from the left that it has the telltale circle where it was rubbing on the plastic cap, having pushed the center contact button all the way into the cavity.

I felt like the Lone Ranger and finally someone else has encountered it.

What I think is happening to make the rotor rub on the cap is the thickness of the pertronix rotating part raising the rotor. When this happened I just went to the bench grinder and removed some from the bottom of the rotor.

As for the other rotors hitting in the cap, just mismatched parts that are being sold for our cars. I have taken off the cap and things looked fine only to find a hard to see ring of copper dust around the inside of my cap. Sometimes it even looked like the cap posts had a grove "machined" into them.

I also suspect this is encountered more than realized because of all the seemingly unexplained problems with engine missing and backfiring reported on the forums. At leadt some of them might be from this.

 

[Dave Russell]

Interesting, I have mentioned having this problem several times in different threads and nobody ever responded that they encountered it.
I also suspect this is encountered more than realized because of all the seemingly unexplained problems with engine missing and backfiring reported on the forums. At least some of them might be from this.

It's been going on with the AH cars for years. With & without Pertronix.
It's not surprising that this problem happens. Cap contact heights vary from manufacturer to manufacturer, same with rotor heights.The problem most commonly shows up when a Pertronix trigger ring is inserted that raises the rotor height. This is the single largest shortcomming of the Pertronix.

A quick check is to place some modeling clay on the high voltage contacts, seat the cap firmly & squarely on the distributor, turn the rotor a couple of turns, & examine the remaining clay thickness for adequate clearance.

Some combinations clear with room to spare, others require trimming the bottom seating surface of the rotor. Checking a couple of spare rotors for adequate clearance ahead of time would be a good idea.

Problems with microscopic cracking of the Lucas branded rotor to shaft insulation, due to over setting the rivet, also happen occasionally. It's been mentioned that carefully removing the rivet & setting the brass contact directly in JB Weld is a good idea on any new rotor of this type construction.

The Mallory distributor/cap/rotor combination should avoid the problems altogether.

 

[RonMacPherson]

As someone else said, this has been a decades old problem. I first encountered it with TRF tuneup specials back in the mid-80's. Got the tuneup special kit, which was about half price of just the Lucas rotor. Put the rotor on, as my old one was getting loose on the shaft; destroyed the lucas cap with the mismatching rotor.

Played the parts house game and found there were about 6 different mfr's at that time. A couple would crossover, but a lot would not, just cause damage or inoperability.

You've gotten good advice on checking the clearance with the Pertronix ignition,(another reason why I prefer my allison/crane shutter wheel optical ignition) recommend bookmark it and refer to it in the future.

 

[roofman]

Does anyone know whom is selling the correct cap and matching rotor right now?

 

[PeterC]

In fact, the rotors 1,2, and 4 are preferred by many, many people for their reliability, and that they do not arc through as #3 will. The issue has been that the Pertronix is the problem. I have had similar experiences as you with 4 and 6 cylinder rotors hitting, unless filed. Without the Pertronix, the height of the rotor is not so critical. Pertronix hasn't fiwed their problem, so the advise to file/sand/grind the bottom of the rotor is the best. Those rotors really are the best available.

Peter C.

 

[DNK]

Ron- The Crane unit too can have problems. When mine was on the road my Crane unit ate Bosch rotors like candy. The only rotor I could run was the Lucas.

I have eliminated all these trouble. Mallory in place now!

 

[Brosky]

It was not the Pertronix or rotor or the cap. Well, the skip or miss was caused by the loose rotor, but what caused that is the key. El Stupido should have checked the side play in the distributor. It was/is the upper bushing. The shaft is moving out of round and that's what causing the hitting. This distributor did not have a bushing replaced because Jeff thought that they looked good.

Something caused it to go, so Jeff wants the distributor back to check it out completely. Hello UPS?

Fortunately, I have plenty of distributors ready to go, so out goes the old and in goes the new. Idle is now set and staying at 850-900RPM and the timing is steady at 16BTDC at idle with a total advance of 38. The car runs just great. Now I finally appreciate the triple carbs.

Time to get to work on the cable conversion / folded coupler page for the website.

Oh, this one has the adjustable timing wheel, circa early models and MG's, via Advanced Distributors. Nice modified curve in this one too! Now I can put that 7/16" wrench away.

 

[roofman]

where did ya get that red cap?

 

[Brosky]

Stock Lucas cap washed down twice with body prep cleaner and painted with Krylon Fusion Spray Paint for Plastic. I let it sit in the sun to bake between coats, but it drys to the touch in about 10 minutes. Really good stuff and it comes in multi colors.

Two coats sprayed evenly gives good coverage. I found this after spending days trying to get a red cap for a 22D, which is just not available.

I use cotton balls down in the plug towers and pull them out with toothpicks after painting is done. Mask the inside with regular tape.

Next one may be yellow to match car and in honor of Accel.