Ignition contact points of Classic Cars

Ignition contact points, which are the means for making and breaking the current flow through the primary winding has been discussed in conjunction with the other components in the system.


Ignition contact points of old school cars

Ignition contact points of Classic Cars

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What s Ignition contact points  


They are made of a very hard and durable metal, usually tungsten, which will withstand high temperatures and wear well.

Considering that the points open and close during each power cycle for each cylinder in the engine – on an 8-cylinder engine running at its rated horse power, say 5200 RPM, they would be required to open and close over 20,000 times each minute.

We can see, then, that points must withstand considerable wear.  Also during operation, the rubbing block on the breaker arm rides against the distributor cam.

This block is usually made of a material that is highly durable, but regardless of the materials, the rubbing block wears, causing a decrease in the point gap setting which reduces the dwell angle, which is the same as retarding the timing.

Normal wear is to be expected, so it is very important that contact points be checked periodically.

Their function is to start and stop the current flow to the primary winding in the ignition coil.

They simply form a switch and are actuated by the distributor cam lobes.

The movable point has on it a block which rides on the cam causing the points to open and close the circuit.   By opening and closing the primary circuit, they allow the primary winding in the coil to induce a voltage in the secondary winding.


The contact points


1-  Are made of a hard durable metal.

2 – Control the flow of electricity to the spark plugs.

3 – Act as a switch to stop and start current flow to the primary winding in the coil.

4 – Form an arc between them to allow a current flow.


Article Source : This article courtesy should goes to Auto Mechanics Autodology – Technical instruction manual by System Operation Support.