Distributor Caps woes

[Shox Dr]

I’m going through Distributor caps and rotors at an alarming rate. This one lasted 3months.

Symptoms are;

Centre graphite nipple errosion along with heavy pitting to rotor cap top. This doesnt always happen. I’ve checked there is good contact between the two when replacing. It still happens but not always

Grey/black arcing marks to the pickups. Rotor shows little tip damage.

Pertronix ingintion and coil. New leads, Plugs NGK B-1 gap set at 35thou. No vac advance. Wiring is new

Any suggestions

 

[The_Yellow_Ardvark]

Have you checked for any sloop in the shaft or backlash on the drive?

Is the pin holding the gear straight?

I had similar issues on a escort. drive me nuts until I found the pin on the gear was bent.

 

[unimog]

standard motor parts
they are ok

 

[Shox Dr]

I rebuilt the dizzy last yr. motor was rebuilt the yr before. Heads just been off and valves lapped in (again)

 

[Bullet2012]

What motor ?

 

[Shox Dr]

GMC 228 l6

 

[500e]

If you have access to a older tuner look at the rotor arm to cap gap.
Short a plug lead down to deck the remaining spike will be the rotor arm gap, do it on all cylinders, the one with the smallest gap is the one to use.
With a judicious bit of squeezing of the rotor contact you can get it down to nothing with a bit more it will actually cut a shallow grove in the cap contacts.
To much & you are looking for a new cap

 

[pedrobedro]

Do you have a ballast resisted coil? What motor is it ?

 

[james butler]

Do you have a ballast resisted coil? What motor is it ?

this was my line of thought, are you using a coil that needs a ballast resister

 

[Shox Dr]

I’m sure pertronix say one isnt required

 

[james butler]

i thought petronix only do the contactless kit with little brain that contols a coil?
my luminition kit works in a similar way but uses the origenal coil and resister.
its worth checking in any case

 

[piman]

Dr Shox,

try resetting your plug gaps back to 25 thou. You are raising the coltage by openeing the gap and stressing the HT side by doing so. It is of no benefit as the spark is less concentrated and it wears out components quicker.

Alec

 

[zeppelin builder]

Dr Shox,

try resetting your plug gaps back to 25 thou. You are raising the coltage by openeing the gap and stressing the HT side by doing so. It is of no benefit as the spark is less concentrated and it wears out components quicker.

Alec

spark is always stronger with a gap before the actual plug there is no earth leakage path ,the coil has to build up more voltage to jump 2 gaps , this set up was proven in ww2 aircraft to be vastly superior
some of the 2 stroke bike racers can be seen pulling the ht cap off a tad to simulate it and magicly clear a reluctant plug
or old farmers used to cut the ht leads in two and join them with a large coat button to get this effect when the old fordson was burning so much oil it fouled the plugs !
with all the arcing going on in the dizzy cap it generates lots of nitrogen oxides which eats the brass bits it is beneficial to ventilate the dizzy with a small round gauze breather on the body "davy lamp style "

the brass bits might be of inferior metal too

 

[Shox Dr]

I increased plug gap from 28, as the plugs were fouling. I took it up to 40, finding 35thou to give the best plug colour.

Pretty sure this was happening before hand.

I’ll drop the gap on a new set of plugs to 30, as see what happens, along with new dizzy cap n rotor

(Dizzy Caps and rotors are peanuts in the states, everyone over here wants 10-15x the price)

 

[Popcorn]

Caps not from a place on 'Gilshill road' is it, had no end of problems there caps ?

 

[jsf55]

I ran pertronix on my rover and blew the unit as it had the wrong coil, fitting the proper flamethrower and and new unit it would last the life of the engine, I had one rotor arm and cap play up but this gave the symptom of a misfire on one plug ! never went above 30 thou on plug gaps tho, be better if you could weaken the mixture a tad, new air filter ?

 

[Shox Dr]

Parts are ‘Standard’



No ballast resistor required. Pertronic flame thrower coil

 

[Wallace]

How old are the ignition leads and are they copper or carbon?

 

[Shox Dr]

18months, copper.

 

[Wallace]

18months, copper.

Is copper recommended for that coil?