Ferrari Mailing List: Re: Mageti Marelli S159B Distribtuor Advice Needed

[Robert W. Garven Jr. (rgarven]

On my original set the rotors pointed to the red mark on the dist.  
spider edge at PM 1-4 and 5-8. and when timed the dist and housing  
mated almost perfectly flush... true the dist only can rotate 10  
degrees but the splines are few in number and I think are about 20  
degrees apart???
When I tried the other spline it was even farther off? I think the  
shafts are different????? I could be wrong, it wont be the first time.  
I am tempted to put the screwed up units back in even at  25 degrees  
dwell and totally erratic and uneven advance curves and it would out  
run any other gt4 or 308
never missed a beat,  idled smoothly, accerated great, never stumbled,  
reved to redline.......  /??&%$# [at] #%

Rob


On Mar 10, 2008, at 12:14 PM, robert_h_bowser [at] juno.com wrote:

> Robert -
>
> I'm doing this from memory...but....
>
> Does sound like the camshaft/rotor connection is off one spline.  If  
> I remember correctly, the rotors in both dizzys normally rotate  
> clockwise (CW).  For the dizzy casing that is rotated all the way to  
> the left (i.e., counter clockwise - CCW), pull the dizzy out until  
> the rotor shaft is just beyond the splines, rotate it slightly CCW,  
> then re-insert into the camshaft.  For the dizzy that is rotated all  
> the way clockwise (CW), pull it out and rotate the rotor slightly  
> CW, then re-insert.  Retime both dizzys.
>
> Perhaps you already are aware, but the Ferrari dizzys are a bit  
> different in a couple of ways.  One, the timing adjustment available  
> by rotating the dizzy is only about ten degrees.  If you need more,  
> you have to pull out the dizzy, rotate the rotor one way or the  
> other, and re-insert.  Two, the advance mechanism does not act on  
> the rotor at all.  All it does is advance the dizzy cam.  So the  
> rotor has a large area facing the distributor cap contacts.  When  
> static timing using the firing marks on the flywheel, the rotor will  
> not be pointing directly at the cap contact.  It will appear to be  
> pointed a bit beyond the contact.  The spark will jump from the  
> trailing edge of the rotor face.  On full advance, the spark will  
> jump from the leading edge of the rotor.  The rotor has to be  
> positioned to cover the full range of timing, from no advance to  
> full advance.
>
> I assume you have already done a check to make sure the cam/points  
> plate is set up properly with respect to the rotor position.  When  
> the points open (e.g., check with an ohm meter), the trailing edge  
> of the rotor should cover the distributor cap contact.
>
> The dizzys do use standard metric o-rings.  I just measured the id  
> of the groove using calipers and bought some of various thicknesses  
> until I got the right size.  I checked my record book, but evidently  
> I didn't record that info.
>
> Hope that helps.
>
> Bob
> '78 308GTS
> '01 Corvette Z06
>
> -- "Robert W. Garven Jr." <rgarven [at] gmail.com> wrote:
> Friends,
>
> I am having a problem and I hope one of you can help?
>
> I have a 75 GT4, running standard ignition with only the R1 points. I
> had a coil wire come loose and the car ran on 1 bank for about 30
> seconds so I decided to replace my spark plugs. While I was doing that
> I have a Sun Distributor Machine that I have not had much time trying
> to figure out so I decided to test my distributors. The PO had a
> distributor overhaul and whoever it was that did the work hot rodded
> my distributors leaving in only two advance weights for each unit. The
> car always ran very well so I kept it like that, however the two units
> were so out of spec that I decided to replace them with a set of
> rebuilt distributors I got from TR about 5 years ago, thinking that
> this would solve all my problem and I also wanted to see how the car
> would perform with factory specs. I spent two days checking them and
> learning how to use the Sun ( which was pretty easy) and everything
> seemed fine, they were a little off but within factory specs. They
> were rebuilt very well by a well know expert and the points were all
> centered etc. Even though I had marked everything when I took my
> original distributors off I decide to make double sure I put them on
> right and rolled the engine around to the PM 1-4 for the rear unit and
> PM 5-8 for the front one.
>
> This is where I noticed something weird. The rotor lined up sort of to
> the line up mark but not as close as the units i took off? Below is a
> picture. When I bought them they did not come as a matched set as they
> were supposed to all be rebuilt to the same specs, and I assumed that
> the units were identical. I tried to time the engine but both of the
> distributors seemed to be so far off i could only get a glimpse of my
> timing marks when they were at their extreme rotation. The only
> difference between my units and these are mine had a red label and
> these were silver with red lettering, however both say S159B. What is
> weird is the front set needed to be rotated extremely to the left and
> the rear set to the right so next week I will try to switch them. I
> this does not work I will try to move their weights into my original
> distributors.
>
> What my question is are these splined shafts identical for the front
> and rear distributors or are the different, or could the later one
> have a different spline due to a different camshaft variation due to
> emissions? I have spent 3 days on this so if any can lend a hand I
> would appreciate it. I think they are different, am I overlooking
> something???
>
> One other weird thing, I ordered the spline o-rings from several
> Ferrari parts places and all sent me ones that were so wrong they were
> up to an 1/8" off. I ended up using my old ones but they are worn.
> Does anyone know the correct size of that o-ring? I would try to
> source it but I have only really worn or wrong ones. What is funny I
> bought a set of metric o-rings with 50 sizes a while back and none of
> them are the right size!! Go figure
>
> The last pic is of my original advance weights with notations that
> Mike F. here on the list added. What is weird is the car ran so great,
> always started never stumbled revved to redline and just screamed all
> this with 25 degrees of dwell and these weights?????????
>
> Sincerely,
>
> Rob Garven
>
> pics are here
>
> http://www.ferrarichat.com/forum/showthread.php?p=137531139#post137531139
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