Setting Ignition Timing on 246 DIno

join the fiat dino yahoo group. we have many guys who work on their own cars who can help you. unfortunately i am not one of them.

 

When you say you have a "3 lobe distributer" does this mean the single point set opens and closes only 3 times per distributor shaft revolution? (I don't see how that could work on a 6-cylinder engine?)

 

You do not need the second set of points with the MSD, what I did when I set mine up was set the motor (206) at 10btdc and watched the spark as I moved the distributor, pull the plug and very very slowly twist the distributor until the spark, lock it down and fire up the car and now use the timing light to properly set the timing, this method should get you close enough to start the car.

The comment about joing the FIAT Dino Yahoo group is a good one if you want to work on your car yourself, they are the same motor. There is in the "files" section of the group a article reprint on installing a MSD ignition in a Ferrari, its a copy of some Ferrari article from long ago and quite good.

 

I've never heard of a way to run the 3-lobe without both sets of points. There are dual-point cars where one set is used only at start up and these can be converted to single-points only but since you have the 3-lobe distributor, unless the MSD you have somehow can convert three triggers into six spark events, I don't know how the car will run without the other set of points.

Otherwise, what you have said about timing light on #3 spark plug wire and the 6 degree mark are correct (though the manual might list an exact rpm for the timing check that may or maynot correspond to the rpm you have at idle).

 

Well if Richard says it cant be done, I defer to him as so far in my experience he has not been wrong on these things.

I have not just the MSD but also the optical pickup so no points on my 3 lobe distributor, maybe that is why mine is working. By the way that article I mentioned at the Yahoo group is on how to install the optical pickup and MSD, not just MSD.

 

The MSD needs one pulse per cylinder. A three-lobed cam using points will cause ignition timing fluctuations. If the optical setup has six slots, or whatever, that should work.

 

Can someone post a picture/drawing/sketch of the "3-lobe" distributor cam and/or a schematic of how the two point sets are wired together? Is there more "electronics" inside the distributor than just the bare point sets?

Since the '72 246OMs show only a one-wire connection to the distributor (and only one active coil), I'm inclined to believe "You do not need the second set of points with the MSD" (i.e., each point set opens 6 times per distributor shaft revolution, and since the point set is only an event trigger with the MSD, rather than part of the high-current conduction path of the coil primary, all is OK.) -- but help me -- I want to learn!

 

Can't post a link to the files section of the yahoo group since it would require your user/pass, I don't remember a "processing" time when I joined but it was a long time ago. If it takes too long, let me know in a PM and I will e-mail you the PDF.

I have the Crane optical in my distributor, its a 3lobe and the optical wheel has 6 slots on it to cause the spark. It still uses the mechanical advance of the distributor. It was very easy to set up.

No experiece with the Pertronix but should be the same

 

If you need a 6 lobe distributor, I have one that I'm no longer using.

Went back to a Euro spec distributor and dual points.

Solved some of my other problems pretty quick.

So, if you want that 6 lobe job, let me know.

DM

 

Some people have had to use the amplifier to make the Tachometer work others (like me) have not, now this is for the earlier FIAT Dino so maybe the Ferrari Dino did not have that problem and also it was not a problem on the later FIAT's. Since yours is a 72 (and not FIAT) you probably will not have a problem but just FYI if your Tach does not work when you get it installed.

Its easy to install all this stuff and with no more adjustment of points it makes maintenance a lot easier, even the timing seems to stay put.

 

DM -- Can you describe this system more? Do you have 2 active coils? Is/Are there one or two wire connections to the distributor?

 

I just finished rebuilding a Dino 3 lobe distributor. It has 3 lobes with a very wide crown on the lobes they stay open a long time. the 2 sets of points are set 15DEG from each other. When one set of points is at the center of the fully open the other set is at the center of fully closed. 3 lobes X 2 points = 6 firing events per revolution. You DO need both sets of points if you want to fire 6 cylinders. They work on piston pairs 1/5 4/3 and 2/6 are pairs, wen one is TDC compression its pair is TDC valve overlap. Here is when it gets interesting. I don't have a distributor machine. set both points to .025inch gap and install dist without upper caing in the way of setting points. Set crankshaft mark to 6deg 3/4 TDC (PM in Italian) (firing point) with cyl 3 at firing point compression and 4 at VO then adjust first set of points base to achieve points open event with testlight then lock down distributor and turn crank 1 revolution so that 4 is at 6BTDC firing then with the distributor locked adjust the second set of points base to achieve testlight open event. you now have points in phase with each other and gapped. Start engine and check with timing light. (Make sure mechanical advance isn't worn out either that what I had to repair)

 

also the distributor lobe has an event just before the points close it opens slightly wider, don't set point gap there set it in the middle of the lobe, I figure the slight wider opening is taking place when the opposite points open (firing event) to help prevent arcing on the open points

 

Here’s my understanding…

Yes, you need both sets of points. Distributors are geared to revolve at 1/2 the crank shaft speed – you get 3 sparks per engine revolution. Each point fires every other spark plug. I believe they used the 3 lobe/2 points to reduce point hop.

Later distributors had 6 lobes and 2 points. But only one set of points operated at a time. For pollution purposes - at lower RPMs a switch would go from one set to the other to change the advance.

Ford did use a distributor with two sets of points in their performance engines to get 2 sparks per cylinder, but that’s not the case here.



Ken

 

Thanks for the info I have also seen some early dual point systems that use 2 sets of points to expand the dwell by making a longer points closed duration by making the first set close first and the second set open last