Breaker Point Ignition
Page created by T July 15th 2008:
- 1 Breaker Point Ignition:
- 1.1 Bosch Distributor Numbers:
- 1.2 The Kettering System:
- 1.3 Distributor Shaft Bearings:
- 1.4 Adjustment:
- 1.5 Using a Dwell Meter:
- 1.6 Worn Out Breaker Points:
- 1.7 The Retainer Tang:
- 1.8 Fitting New Points:
- 1.9 Replacing the Distributor in the Engine:
- 1.10 Condenser:
- 1.11 Capacitor Testing:
- 1.12 Coil:
- 1.13 Ballast Resistance:
- 1.14 Braided Grounding Strap:
- 1.15 Timing the Engine:
- 1.16 Tune Up:
- 1.17 Links:
- 1.18 Terms:
Breaker Point Ignition:
Breaker point ignition was phased out of Holdens with VC Commodores and WB's. Routine adjustment and ultimate replacement of the units was caused by burning of the point faces and the wearing out of the rubbing block. A failing Capacitor made the points burn out faster.
Bosch Distributor Numbers:
7421198 This is from an EH Distributor. Thanks Wombat for the info.
The Kettering System:
This type of ignition is called The Kettering System named after the Delco inventor of it.
Distributor Shaft Bearings:
Check these for wear. If there is excessive play in this shaft the dwell will not be stable and rough unpredictable running will result. Also check the endfloat.
Feeler gauges could be used to set the initial gap but a Dwell Meter gave the best results. A Dwell Meter displayed the ratio of on to off times of the points on a scale. While it's easiest to set the Breaker Point Gap with the Distributor removed from the Car, this isn't always practical.
Using a Dwell Meter:
A Dwell Meter is a device which can be used to both check and set breaker Points.
A scale on the meter will indicate whether the points are due for replacement by measuring the resistance between the Point faces. If the meter shows the Points to have excessive resistance the Points should be replaced. If the Dwell angle is too small, the Point Gap is too wide. If the Dwell angle is too wide, the Point Gap is too narrow.
Dwell Meter instructions are at the following link.
Worn Out Breaker Points:
Old Breaker Points will be considered worn out when the faces of the Points themselves are burned. The Pivot Post can also have excessive wear which will prevent the Points from making square contact with each other. The small Rubbing Block which contacts the Cam Face can wear out too. If the Rubbing block breaks off or completely wears away the Points will short out against the Cam face preventing Spark from being generated.
The Retainer Tang:
The Retainer Tang secures the Breaker Point Plate to the Distributer and allows it to rotate. It can wear and become loose. When loose it will cause the Dwell to be unstable as well as the Ignition Timing. Retension it by lightly tapping down on it. When set correctly there should be no play and the Breaker Plate free to rotate. Smear grease on it to allow the Breaker Plate to rotate easily without wearing. ===Distributor Overhaul:===It's easier to fit and set the Breaker Points with the Distributor removed from the Car. To do this place a chalk mark between the Distributor Body and the Engine Block. Place another chalk mark where the Rotor Button points to the Distributor Body. Unbolt the Distributor and place the Distributor in Vise with Soft Jaws to prevent the Distributor Body from being damaged.
- Don't* allow the Engine's Crankshaft to rotate until *after* the Distributor has been reinstalled in the car or you will have to retime the Engine from scratch. Unscrew the Breaker Points and remove them. Use WD-40 to clean all the moving parts inside the Distributor.
Make sure that the Balance weights are clean, oiled and expand and spring back into their original position easily.
Make sure that the Vacuum Advance Module is free to move by applying Vacuum to the Pipe that feeds it. With Vacuum applied the Distributor Advance Plate should rotate in an anti-clockwise direction. With Vacuum removed it should spring all the way back to its original position. Install the new Breaker Points and fit the screw to them but don't fully tighten it as yet. Leave the screw only tight enough that the Ground Point can be moved with slight effort.
Rotate the Distributor Shaft by the gear until the widest opening point for the Breaker Points is reached.
Position a Feeler Gauge between the ground and moving Point of the Breaker Points.
Fitting New Points:
When new points are to be fitted, follow any Instructions from the Manufacturer.
If there are no Instructions new Points should be inspected when removed from the packaging.
The Point faces should be washed in Solvent to make sure there is no Oil on them. Any Oil present will
make the Point Faces burn out rapidly. Both the Point faces must contact each other squarely. If they don't contact squarely, the Ground Point should bent
to fix the problem. if the Points do not face each other squarely current carrying ability will be reduced
and the Point will wear out faster as a result.
Replacing the Distributor in the Engine:
Make sure the round paper gasket is fitted to the Engine Block on the Distributor Hole. Lower the Distributor into the Engine. As you do, make the Engine Chalk Mark and Distributor Chalk Marks match. As the Distributor is lowered into the Engine Block the Distributor Shaft will be rotated clockwise about 15 degrees by the spiral of the Distributor Gear. You will have to position the Distributor Shaft about 15 degrees anticlockwise of your Chalk Mark to make the marks line up properly. If the marks don't line up when the Distributor is in place, remove the Distributor, rotate the Distributor Shaft anticlockwise by an appropriate amount and reinstall it. Repeat the process until both the Chalk Marks line up again.
The proper name for this is the Capacitor.
To test the Capacitor: 1. Hold the Breaker Points open somehow (rotate the Distributor Shaft until they are open or place paper between them so they can't make contact). 2. Isolate the Distributor Wire from the Coil and anything else that connects to it. Leave the Capacitor wired in place inside the Distributor. 3. Connect the Distributor directly to the Battery by connecting a piece of Wire between the Battery +ve and the Distributor Connection. The Capacitor will charge up instantly. 4. Discharge the Capacitor by removing the Battery end of the Wire from the +ve and shorting it to the Distributor Case. It should Spark convincingly. If not it's dead and needs replacing. The Capacitor is vital in creating a Spark strong enough to fire inside the Cylinders.
The Coil can be tested to see if it will produce a 3/8" Spark in Air. If not, it's failed. Be aware that if it can produce such a Spark it may still be faulty under Load.
The Ballast Resistance can burn out. This is characterised by the Engine firing under Cranking but stopping as soon as the Key is released to the ON position.
Braided Grounding Strap:
This can break and cause poor Electrical Contact resulting in weak Spark.
Timing the Engine:
With the Distributor back in place the Ignition timing will now be slightly advanced or retarded. The Ignition Timing needs to be done after replacing the Breaker Points because wear in the points changes their opening position.
At every Tune Up, remove the Rotor Button and put 3 drops of Engine Oil into the centre of the Distributor Shaft and onto the foam Pad in there. This lubricates the Balance Weights.