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308 Distributor R1/R2 problem

Discussion in 'Technical Q&A' started by marks308GTB, Sep 1, 2004.

  1. marks308GTB

    marks308GTB Karting

    Jun 6, 2004
    114
    Los Altos Hills, Ca.
    Full Name:
    Mark S.
    I am having a problem with the distributor points R1/R2 setup on my 76 USA double distributor car. I have tried to find the answer in the archives but no success. So please bear with me as I try to describe the problem. Driveability at low rpms is a little rough and sluggish. Above 3000 everything is fine.

    I checked the microswitch setup and found that the wire leading to the R2 terminal on both distributors was shorted to ground permanently no matter which position the switch was on. The switch itself checks out fine. So I disconnected all wires to the R2 terminals and found that the R2 terminal on the rear distributor is not grounded, but found that the R2 terminal on the front distibutor is permanently grounded. The condensors appear to be fine. I have not pulled the dist. caps yet. I need to get some education first!


    Questions:

    I thought that the operation of the microswitch was supposed to connect the R2 terminals to ground so that the R2 points were in operation. How can this be if the front distributor R2 terminal is already permanently grounded??? What this appears to have done is to have put the R2 points into permanent operation on both distributors given that they are connected together.

    Why is the R2 terminal grounded on one dist. and open on the other???

    If this is incorrect, has someone or some failure caused the R2 terminal on the front distributor to ground out?? Has this potentially been done purposely so that the advanced point set is always turned on?

    If it is supposed to be this way, then I am completely lost and would love some help.

    Thanks very much,
    Mark

    PS Is the microswitch in the "open" position at idle, then closes at 4000 rpm or is it supposed to be "closed" at idle then opens at 4000rpm?
     
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  3. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,389
    B.C., Canada
    #2 Peter, Sep 2, 2004
    Last edited by a moderator: Sep 7, 2017
    However it is set-up on your car - in a confusing way - The R2 points should be "on" (closed circuit) along with the R1 points. What this does, is that the R2's add 3 more crank degrees to the timing of the R1 points at slow speeds up to 3900 RPM. After that point, the R2 points are turned "off" ("open" circuit) by the throttle shaft paddle lifting off of the microswitch in its travel.

    In any case, the leads of the R2 points should be connected to the R1 terminal and the base of the points (its ground essentially) should have another lead going to the "R2" terminal on the distributor body. Its this lead that should go to the microswitch.

    I never had this system on my car, but I'm just going by what's in my workshop manual. The photo below shows my distributor when it had only the R1 points. As you can see, where the R2 points used to be is the old plastic insulator.

    Hope this helps in some way.
    Image Unavailable, Please Login
     
  4. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,283
    Texas
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    Steve Magnusson
    "Why is the R2 terminal grounded on one dist. and open on the other???" -- This is definitely not correct/normal.

    One thing that adds a lot of confusion to this whole subject IMO is that "the R1 terminal (stud)" and "the R2 terminal (stud)" are two different kinds of electrical connections even though they have similar names:

    the R1 terminal is the connection to the moveable R1 point contact

    the R2 terminal is a connection to the (insulated-unless-the-microswitch-is-closed) R2 fixed point contact

    (the R2 moveable point contact is connected to the R1 terminal and the R1 fixed point contact is always connected to ground via the distributor body)

    I believe the schematic/figure on page L13 in the WSM is correct and would suggest that you go by that.

    One other point is that the 3900 RPM crossover point from R1+R2 operation to just R1 operation that Peter R. mentioned is for the 159A distributor advance curve (the desired RPM crossover for the later 159B advance curve is lower).
     
  5. FourCam

    FourCam Formula Junior

    May 19, 2004
    401
    Loveland CO
    Full Name:
    Cameron MacArthur
    My understanding is that the second set of points is strictly to help reduce emissions at idle. I have my microswitch set to "break" just off idle--way before 3900 RPM and the engine not only runs great, but also passes emissions. In other words, the microswitch is closed at idle and opens just off idle. Try it, you'll like it...
     
  6. Sophia

    Sophia Formula Junior

    Aug 17, 2003
    298
    Dash Point/Federal W
    Full Name:
    Peter Barbin
    Mark, I'm still running dual points too. And I was running into a bit of trouble as well. I hadn't progressed to the poor running phase but I'm sure I was heading that direction.

    I found getting to the distributors profoundly easier to access by removing the left rear wheel and fairing...you can also get to the coils to inspect the wiring there too. See vTach Jumping/Corrosion.

    PeterB.
     
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  8. marks308GTB

    marks308GTB Karting

    Jun 6, 2004
    114
    Los Altos Hills, Ca.
    Full Name:
    Mark S.
    Thanks, everyone for this help. I am beginning to see a possible explanation for my problem. First issue is that I have not been able to get my hands on the workshop manual, although I am still trying and may have found one.

    Anyway, from your discussions and from the photo that Peter posted, it looks like there is a possibility that the R2 points in my front distributor is missing the plastic insulator plate that the points sit on. With that plastic plate missing, the R2 points would be permanently grounded keeping them in the circuit all the time. This would make the operation of the microswitch redundant. (Not sure what effect this would have on operation. Seems like both points are in the circuit all the time....is that giving me too much or too little advance at 4000 rpm?????)

    I am going to try to pull off the dist. cap and see what is going on in there.
    Thanks for the hint on removing the wheel and fairing.

    I would feel better if I had a copy of the WSM in my hands, so may wait a few days to see if I can get one.

    Thanks again,
    Mark
     
  9. Steve Magnusson

    Steve Magnusson F1 World Champ
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    Jan 11, 2001
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  10. 4Webers

    4Webers Formula Junior

    Nov 12, 2003
    276
    Texas
    Full Name:
    Darrell
    What FourCam said is correct - the microswitch should only be closed at idle, and it should open immediately when the throttle is opened the slightest bit. The manual even warns that operating the engine at high rpm while running on R2 points can be dangerous to the engine, since it may not have adequate advance. I have been maintaining my car to run on both R1 and R2, but it is a real PITA, so now that I don't have to pass emissions I am going to disable the R2 set.

    Going through the wheel well may be a little better, but you should just plan on pulling the distributors if you need to do anything to them. Just be SURE to get the engine at compression TDC, making sure that the rear bank (1-4) rotor is pointing to the little red scribe in the housing, before you pull one. I also recommend only taking off one distributor at a time until you are sure of what you are doing.
     
  11. marks308GTB

    marks308GTB Karting

    Jun 6, 2004
    114
    Los Altos Hills, Ca.
    Full Name:
    Mark S.
    Latest....

    I was able to order the WSM and will get it next week. In the meantime, thanks for the link to Jenkins since it allowed me to preview the situation. I now understand what is happening, although since I have not yet pulled the dist. cap, not sure exactly what is the source of the problem.

    I know for sure that the R2 points on one dist. are permanently grounded and therefore are in operation all the time. This is bad news for high rpm operation. So, I have to fix this. I am suspecting, as I mentioned earllier, that the plastic insulator plate underneath the R2 points is missing, cracked, etc. and is allowing the points base plate to touch metal on the inside of the dist. (This situation renders operation of the microswitch moot until I get this fixed)

    So, next question. Unfortunately, the WSM does not give me any hints as to whether or not I can remove and replace the R2 points without having to remove the distributor which I would rather not do. Also, its not clear that I can even remove the distributors without pulling the engine. (It does not look like removing the left rear wheel and fairings is going to buy me very much).

    Question: Can I remove/replace/fix the R2 point set on the front dist. without removing the distributor??? Can I correctly set the dwell and phasing even if I CAN replace the point set?? Is it folly to try this....in other words should I just pull the distributors(assuming that that can be done without pulling the engine). Or just take the beast to a reliable Ferrari mechanic??

    Thanks, your help on this F-chat has been excellent!
    Mark
     
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  13. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,951
    Austin TX
    Full Name:
    Brian Crall

    Getting the distributors to work proper is really the key to getting a 308 to run well. In addition to the points you should clean and relube the advance weights,test the advance curves on a dist machine to, 1, make sure they are working properly and, 2, to make sure they are working the same. Getting the phase, dwell and R2 retard correct without being on a machine is very difficult. Also the R2's function is not just for lower emissions in the strictest sense. The US car has so much air entering the motor below the carbs through the various hoses from charcoal canisters etc that to get a good, stable idle the ignition must be retarded to achieve that. The carbs are not able to efficiently lower the air flow to the required degree and still meter worth a damn. So to make the carbs work proper the distributors have to be spot on. Yes I would take them off and bring them to somebody that really knows them and has a distributor machine.
     
  14. robertgarven

    robertgarven F1 Veteran
    Rossa Subscribed Owner

    Feb 24, 2002
    5,082
    Ventura, California
    Full Name:
    Robert Garven
    My gt4 passed CA emissions 3 times with no r2's and a tubi (but with smog pumps belts connected). I have no problems, with a very steady idle at 1000 rpms. I have an Allen machine but right before Monterey I had a small leak so I removed both Dist. and reset the points with a feeler gauge replaced them and set the timing and it runs great 650 miles with out so much as a hic-cup. The exhaust will kill a pedistrian at a crosswalk though :) I will be rebuilding them soon and will post to the board. My suggestion if you can is remove all that crap but........

    Rob
     
  15. gerard.hansen

    gerard.hansen Formula Junior

    Jun 29, 2004
    665
    Hattiesburg/Petal MS
    Full Name:
    Gerard D. Hansen
    What should the point gap be?
     
  16. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,389
    B.C., Canada
    0.012 - 0.015"
     
  17. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,389
    B.C., Canada
    It states that high RPM for those cars equiped with the 159B's later in the WSM (page O 8) and also in the Owner's Manual...
     
  18. fatbillybob

    fatbillybob F1 World Champ
    Consultant Owner

    Aug 10, 2002
    19,034
    socal
    Rifledriver is correct. In addition, You have to get both distributors off the car which can be done without pulling the motor. Put the 1-4 at TDC in compression stroke and then take the distributors out. This makes for easy replacement and a known static timing position. You need to find someone in your area with a sun distributor machine to set up the units. You need as routine maintenance to replace the distributor shaft bearings, cam shaft seal on the distributor shafts and set-up so that the advance curves are equal on both distributors. I ran my car on one set of points and nixted the smog points. The car runs fine this way but may not pass smog in your state. You can also swap out the points for a crane allison xr700 optical pickup set up with one distributor acting as a master and the other a slave. You do it by getting two xr700 units with both pick-ups in one distributor. If you do this it is difficult to go back to points since you have to dril off some parts in the old unit. You will then still use two coils and the routine spark plug set.
     
  19. marks308GTB

    marks308GTB Karting

    Jun 6, 2004
    114
    Los Altos Hills, Ca.
    Full Name:
    Mark S.
    OK.

    That clears it up. The distributors are coming off and will be rebuilt. Will take them to a known Ferrari specialist.

    Thanks,
    Mark
     
  20. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,283
    Texas
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    Steve Magnusson
    No doubt that you are factually correct Peter, but I believe that that is an oversight, or maybe it's peculiar to the introduction of that specific configuration shown (thermal reactor with 159B dists) -- anyone know what year(s) they had this on 4/B/S? In the later cat-equipped '78 OM page 75:

    "-The passing from the retarded point to the advanced... ...must happen as soon as the throttles of carburetors are moved from the idle position."

    It's sort of interesting that completely removing the R2 points is like having the crossover occur at 0 RPM so I think there's some logic to FourCam's suggestion even with 159A (i.e., get the "benefits" of the retarded idle, but don't suppress the low/mid-band advance).
     
  21. Rifledriver

    Rifledriver Two Time F1 World Champ

    Apr 29, 2004
    26,951
    Austin TX
    Full Name:
    Brian Crall
     
  22. Peter

    Peter F1 Veteran
    Rossa Subscribed Owner

    Dec 21, 2000
    6,389
    B.C., Canada
    It may be that these earlier cars needed to carry retarded timing for so long in the rev range to help clean up emissions and that later cat cars needed it just at around idle, with the cats doing most of the work afterwards from idle. Could that be the reason why they list the same rev point for switch-over for the earlier cars?

    In any case, the off-idle switch-over sounds like it works quite well for FourCam and it does make sense the way you put it Steve.
     
  23. gerritv

    gerritv Formula 3

    Jun 18, 2001
    1,400
    St Catharines
    Full Name:
    Gerrit
    Hi
    The 1974 GT4 OM does not specifc the point at which the R2 points are disabled. The 1975 NA OM specifies that it occurs when accelerator is depressed. It also warns that it is unsafe to allow the R2 points to be active very far into the RPM range. If you want to keep the R2 points, I recommend getting a copy of the 1975 NA manual from the Ferrari Owners site (remember this is free). For whatever reason the NA manuals are far more detailed in the settings. Also interesting is that for the Euro cars the switch is at the gas pedal, for NA cars it is at the carbs.

    Gerrit
     

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