Did You Get the Points?

We will delve in to the world of the distributor with points in this article. I know that many are switching over to the pointless ignition systems for more stability and power, but there are some of us that are purists and stick with the points. I am going to reveal some secrets here that will get you a lot of mileage out of a set of points that you may not have heard of. We are going to get more than 15,000 miles out of a set of points or more, if you are clean in the installation and follow the directions.

You will need some  basics: a type of cleaner in a can, a tube of cam lube, a clean set of thousandths (or metric) feeler gauges,  a Phillips (cross point) screw driver if needed, a flat blade screw driver and a set of small 8, 7 or 6 millimeter wrenches depending up your particular distributor, a an oil can or way to put oil in a small hole, test light for circuits and a quality timing light. You will have to source for a set of correct points and condenser to have on hand to do this job. If you have a “dwell” meter your are truly blessed.

Here is a simple description of a distributor and moving illustration that will give you a quick over view of how this works. Distributor.

For this article I am using an “original as used” Bosch JF4 distributor as used on 1600 Veloce spiders and 1600 Sprint Speciale’s.

JF4distributor

A JF4 1600 Veloce Distributor (click to enlarge)

Points are nothing more than two metal surfaces that touch each other to close a circuit and fire a coil. The cam on the distributor shaft opens the points for a period of time. You can think of the cam as a ramp. The points are closed at the bottom of the ramp. As the engine turns the distributor shaft, the  cam follower (A), rises until it hits the peak of the cam, the points will open. When the points open to disconnect the ground connection you get instant spark. The condenser serves to enhance the spark by greatly increasing the voltage to the input of the coil. It does this through a sudden electrical surge and a high frequency ringing effect, bringing the voltage as high as 300 volts for input to the coil immediately after the points break. This opening of contacts fires the coil sending a spark down the center ignition wire to the center of the distributor cap. The spark jumps the air gap via the rotor and goes to the corresponding cylinder spark plug. 

Internal workings of a Bosch JF4 distributor

Internal workings of a Bosch JF4 distributor The letters correspond to a part of the article (click to enlarge)

DISTRIB

Illustration of the internals of distributor points showing cam lobes with the points open.

You must have the correct points and condenser. This is essential. The points are a stainless steel spring with two hardened steel contacts at the end. If you choose the wrong points, the spring could be too weak and at high rpm the points will float. In other words, they stay open to long because things are happening so fast they never really close completely allowing the coil to not fully recharge. Then the engine starts to miss. Choose the wrong condenser, you will burn the points. The condenser is to minimize the spark at the points when the points open. This is what “burns” the points. The ignition contact points serve as a trigger for the ignition coil. A small current flows through the points momentarily when they close, and this is what tells the spark coil exactly when to release the jolt of electricity that powers each spark plug.

pointspartnmbr

Bosch Distributor Repair Kit

points pointschart

Every time you change points you should change the condenser so they are a matched set. This is an original set of Bosch points, condenser kit. I have enclosed the part number so you can see if you can source something like this. Try checking at a VW shop to see if they carry something like this or the correct parts. There might even be a cross reference number. I am trying to find a reputable source for points/condensers/cap/rotors. If you know of a source, please leave comments below. I will add them to this article at a later date.

To get ready to install a set of points, you will need to remove the distributor cap and wires. Just two clips or screws will allow you to do this. Look inside the cap for “carbon tracks” between the copper posts/contacts as this indicates a cracked distributor cap and the electricity is going from post to post, creating a misfire in the engine. Replace this cap. Check the contact posts for excessive corrosion. If in doubt, replace the cap. You can use some sand paper on the flat faces to restore them to a clean surface. Any corrosion here is an impediment to a strong electrical pulse getting to the spark plug. Check the rotor for corrosion as well. You can use some fine sand paper to restore the copper/metal tip. Just don’t take off a lot of material as you would be increasing the gap, changing the impedance of the spark and making the spark jump a larger gap.

If you undertake this task, you do so at your own risk. It is an easy thing to do, but things do go wrong.

distbracket

Description of lock down bracket

To install a set of points in a distributor: Remove the distributor from the engine block. Usually there is a 6 mm nut holding the lock down bracket in place. Remove the distributor O-ring seal from under the bracket and replace it back in the block or install a new one. You probably have left the cap in the engine compartment with the plug wires still attached. Check the rotor tip for excessive spark wear and the inside of the distributor cap for arcing marks. If they are excessive, replace both as a matched set. Sometimes you can sand smooth the tip of the rotor and clean the distributor cap contacts, but then you are creating a larger gap for the spark to jump. If in doubt, change them both as they are not that expensive.

condenser

Bosch condenser part number for a JF4 distributor

Inside or outside of the distributor you will see a condenser with a wire on it with a screw to hold it in place, a bolt going through a hole with  insulating going through the distributor body and a retaining nut. The points sit on the distributor plate with a screw to hold it tight. Remove the condenser by removing the retaining screw, and loosen the nut to slide out the spring. There should be insulation between the body and the points to keep them from touching so they don’t ground out.

Remove the retaining screw (between points B & D)  and loosen the bolt (C) to remove the spring allowing removal the points. Notice the bottom of the points, as there is a bit of a pin sticking out. This pin goes in a hole in the mounting plate to be able to rotate the points to set the clearance.Clean the distributor plate of any grease and grime so it is clean. Lube the counter weights so they slide freely. If there is an oil hole with a cover, open it up and insert a few drops of oil to lubricate the shaft. Clean the outside of the distributor to be as clean as you can.

About the counter weights…they advance the points to advance the spark curve as the engine revs up. They should return to their bottom setting freely. If they hang up so does your idle! Hmm, you think your high idle might be because of your counter weights not bottoming out? Maybe. They have springs that pull them back so be sure they are connected properly. I have taken apart distributors to find plastic retainers missing, springs missing or hanging loose and retainer clips for the weights missing which allows them to float up and down on their mounts. All of this is not good. The springs are rated by tension and not easy to replace. The same with the weight retainers as they are not available unless you have a drawer full of spare distributor parts.

Clean the cam especially clean as this is where dirt can get trapped in the cam lube and wear the cam down. The only solution here is to replace the distributor shaft.

Install the set of points. There are two kinds of points for Alfa’s. Single one piece points that just drop in and the two piece like in the Veloce distributor. The later Veloce distributors  use a one piece set of points. In the Veloce you have to mount the one set to the base plate and then slip the other half down over the point shaft, and hook up the spring to the bolt that passes through the body.

Here is one of those techniques I learned years ago on my own car. You must “polish” the points before you install them. I use a clean cotton T-shirt to do this. If it is one piece it is easy as you put your points over a fold in the cloth and drag them up and down using the natural spring tension in the points to push against the cloth. What this does is micro-polish the point surface to a shine, removes grease or protective films from the factory to prevent rust while sitting on the shelf.

points diagrahm

Illustration of point contact alignment

When you install the points you must make sure that the contacts line up perfectly. You can use a small set of needle nose pliers to tweak the angles so they mate perfectly. If they are not square to each other, then what happens is you get premature points wear or arcing. Twist the distributor shaft a few revolutions and make sure the point faces are still square to each other. See the above picture of the point contacts and how they are perfectly aligned.

Now you need your feeler gauges. Find the .018 thousandths feeler gauge. Make sure it is super clean as you are going to touch the contacts to measure the gap between the two contact surfaces when the cam is at its highest and the points open to this clearance of .018″. The period of points closure is specified by the ignition system designer and is typically expressed as degrees of distributor rotation. In a four cylinder engine, the angle between each ignition cam lobe is 90° and the period of points closure or “DWELL” is usually a bit over 45° of distributor rotation. If the points are closed or open more than the prescribed clearance, you change the dwell angle and your distributor curve changes as well. Electronic ignition changes all of that by setting the clearance once and it is correct forever as there is nothing to wear out.

Set the cam follower on the highest point of the cam lobe and open/close by adjusting the gap on the points until you get a slight drag on the feeler gauge as you pass it between the point contacts.  You use a small screw driver to open/close the points by twisting the points base left or right (D) . Use just enough tension on the screw to hold the points so you can measure the tension on the feeler gauge. You don’t force the feeler gauge between the contacts. If you don’t get a slight drag you have the points to far open.

Once you set the drag on the points, tighten the set screw. Make sure the point faces are still square to each other and remeasure the point gap. Sometimes setting the screw will change the clearance.

distributorlubeTake a small dollop of cam lube from the tube on the end of a small screw driver tip and apply it to the high points of the distributor cam. Distributor cam lube comes from different manufacturers, but because of a small demand as car manufacturers have moved to pointless ignitions, this stuff is not on every shelf in a parts store. This cam lube is a special silicone grease that is designed to last a long time and not melt off under engine heat. Twist the distributor cam several times to coat the shaft and the phenolic block. That is all it takes to lubricate the cam.

Install the condenser wire and coil wire to the appropriate locations and secure the locking nut/bolt arrangement.

Install the rotor. If you can find a rotor with out the resistor material in the head, your better off as you will get a hotter spark. The resistor is to help prolong life of the rotor and cap so they don’t burn the contact edges. It can in a weak spark condition create a situation where the car may not start.

dist_offset

Note: there is offset in this distributor base

Re-install the distributor by setting the distributor so it sits completely down in the hole. It is possible to set the distributor but the off set cam is not seated properly in the top of the oil pump  letting the distributor sit up higher than it is supposed to. Rotate the distributor shaft until the distributor is fully seated. If you remember where it was when you removed it, you will be ahead of the game. Install the 6 mm nut/washer.  Set the pinch lock bolt so you can turn the distributor, but not so loose it will move on its own. Re-install the distributor cap and hook up the negative coil wire to the connector on the distributor. Clean this contact with DeOxit D5 before installing, for a like new electrical contact surface.

Suggestions? Leave your appropriate comments below and I will respond accordingly.

Watch for the next article on how to set your distributor timing…

Thanks to the mgaguru website for information in the writing of this article.

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About alfadoc

I have been involved in Alfa Romeo cars since 1970 when I bought my 1600 Veloce spider. It was in 1972 that I started the Veloce Register for 1600 cars. It was in 1998 that I added the Sprint Veloce, 750 Spider Veloce and Sprint Speciale registers. Currently I own 4 Alfas: 1600 Spider Veloce, 67 Super, 71 GTv and a 94 164Quadrifoglio.
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