The Fiat Dual Point

Tune-up Page!

This is an enthusiast maintained page designed to help those of us who own a Fiat with the dual point distributor. You should just print this now and use it when you go to tune up your car.

Background:

Fiat used a dual point distributor begining in 1973 on the 1592cc 124 Spiders and Coupes. Then, in 1973 on all 124 series cars through the 1978 model year. This same system was used on all the 131s and most Lancia Betas from 1974 through 1978. It was replaced in 1979 with the Marelli electronic ignition system. Many of the earlier cars can be converted to the newer electronic by replacing both the distributor and coil/module pulled from a newer car with no trouble. In my own opinion a properly tuned point system can match the performance of the electronic system on a carburetor car, but will require more routine maintenance.

Dual points do not operate simultaneously. One set is used for starting, and the other for running. The starting set provides 10 degrees of additional spark advance during starter cranking. The running set returns the spark timing to top dead center. The starting set cuts out and the running set takes over when full oil pressure is reached. The relay switch-over is also activated by a thermo switch which is located on the under side of the intake manifold. It activates when full oil pressure is achieved and the water temperature in the manifold reaches 46 deg. F.

There are other methods that essentially end up with the same result, but this method worked well for me on my '78 Spider. Expect to spend about two hours going through this if you haven't done it before.

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Removal/ Installation

1. Remove the two distributor retaining screws. Remove cap.

2. Pull straight up on the rotor to remove it.

3. Remove the condenser and breaker point lead wires. The wire for the running points is green and the wire for the starting points is green with a black tracer.( remember which set had which wire, so you know which is run and which is start)

4. Remove the screws holding the condensers and replace the condensers. In my experience condensers will far outlast points, but you might as well do it now . Remove the retaining screws for the points and remove the points. Install new points. Snug but do not completely tighten the screws yet.


5. Turn the engine over by hand or bump it with the starter until both point sets are open with their rubbing blocks on the high points of the distributor cam lobes. Check the point gap with a feeler guage. If the gap is correct the feeler guage should pass through with just a slight drag. Remember the gap is different for the run set and the starter set.

6. Adjust the points by inserting a screwdriver in the adjusting slot and twist it one way or the other to change the gap.

7. Once the gap is correct or close reinstall the rotor and cap. Check dwell angle and ignition timing.

You're NOT done yet. Keep going!

Adjustment

Ok, thats the easy stuff now is the part that makes the car run like new. I should mention that you should apply a small amount of cam lube to the distributor shaft cam lobe to prevent quick wear of the rub block on the points.

Dwell Angle

The dwell angle is the number of degrees of distributor cam rotation through which the breaker points remain fully closed (conducting electricity). Increasing the point gap decreases the dwell, while decreasing the point gap increases the dwell. Remember that while you are cursing at your car trying to adjust that gap. Dwell angle should always be checked after adjusting or installing new points.

Using a dwell meter (most tachometers are combo dwell meters) connect the negative lead to a known ground and the positive lead to the primary distributor connection at the coil( could be labeled on coil as B+) On all models with dual points , both sets must be checked independently. To check the running set, first locate the ignition mode selector relay. Trace the green and black/green wires from the distributor until you locate it.(on my '78 it was on the panel under the glove compartment. It has 5 prongs on it). Remove the relay from the plug and insert a jumper wire between the power side and the run side as shown in drawing.



Start the engine and observe the dwell measurement. If the dwell needs adjusting remove the distributor cap and adjust the point gap(remember a larger gap means a smaller dwell#) To check the dwell on the starter set of points, leave one end of the jumper wire on the power side of the plug and connect the other end to the starting side as in diag. You should be very picky about how close the run set is set to specs. It will make a difference of night and day. You'll have to do it several times to get it right. Start the engine and repeat the procedure for the start set if needed.

Once you have set the dwell proprely reinstall the relay. The ignition timing must now be checked. Setting the timing tells the ignition when to fire in relation to Top Dead Center of piston travel. A one degree increase in dwell results in the ignition timing being retarded two degrees and vise versa.

Click to check for your Specifications:



Run set dwell angle: 55 degrees +/- 2 (53-55 worked best for my '78 spider) Start set not as critical but about the same as run set.

Good luck! Expend to spend a couple of hours if this is the first time you've done this.