Point Type Ignition Systems
Replacing The Points
Now that we know what the parts are and what they do, lets talk about replacing them. Replacing the points and condenser are very easy and you should always put in a new condenser with new points. I always took the old points and condenser and put them in a zip lock bag and kept them in my car. If I had a problem I always had a set that I knew would work and get me going again.
All you need to replace the points are some basic tools, a magnetic screwdriver, feeler gauges and a dwell meter.
First remove the old points and condenser. Use a magnetic screwdriver to remove the screws. I think every mechanic has dropped those little screws inside the distributor at one time or another. I know I have. Once you have them out, install the new ones but don't tighten the points completely, just snug them up. Most new points come with a little vial of grease. Make sure you clean the distributor cam and apply this grease. If it didn't come with grease, use a dab, a small dab, of white lithium grease. This will keep the rubbing block from wearing out in a week and a half.
Setting the Point Gap: Getting the best gap between the points is essential for proper engine performance and reliability. Set the points too wide and the spark plugs don't get enough juice. Set them too close and the engine works fine for a few miles until the points are burnt beyond use.
Most cars had a point gap of about 0.019", or the thickness of a matchbook. Some were set higher or lower so check your manual to be sure. To measure the point gap, you need a set of feeler gauges. Adjusting the point gap is a simple process, but it takes some practice to get the hang of doing it properly. First, make sure the rubbing block is on the high point of one of the cam lobes. If it isn't, you will have to turn the engine a little bit in order to turn the cam.
Once you have the rubbing block on top of a lobe, you can measure the point gap. Loosen the screw that holds the stationary point bracket to the base plate. Not completely, just enough so that you can move the bracket by inserting a screwdriver tip and twisting it Adjustment is a matter of trial and error. Move the stationary point out a bit if it was too close, tighten the holding screw (not too tight), and measure the gap. If it still isn't right, try again. The feeler gauge should have a light drag when the points are properly adjusted. This is where practice and patience comes in handy.
Dwell Angle: The dwell angle is the number of degrees of rotation of the cam/distributor during which the points are closed. During each rotation of the cam/distributor, the points must open and close once for each cylinder. The points must stay closed long enough to allow the coil primary current to reach an acceptable value, and open long enough to discharge and produce a spark.
Many mechanics like to check the dwell measurement with a dwell meter after setting the points. I know I do. There are some who say you don't have to. But it is a good way to check the point gap and make sure it is right.
I know many mechanics, myself included, that set the points by dwell alone. It is a perfectly acceptable and accurate way of adjusting the points. In fact, most all GM distributor caps have a little door that allows access to the points so the dwell can be adjusted while the engine is running. On engines that don't have that access you need to be a little more creative. What I do is remove all the spark plugs from the engine, set up the points, turn the key on and crank the engine while adjusting the point dwell. Once it's set, I lock them down and finish the tune-up.
When I set the dwell, the spec is given as a range. I always set the dwell to the low end of the range. This way as the points wear, the dwell stays in range.
Well, that's it. It's not that difficult to do. And if your car has dual points, don't be scared. Just treat them as individual points when setting them up and you'll be fine.
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