Now The !@#$% Is Crossfiring!

Discussion in 'Technical Q&A' started by donaldh2o, Mar 16, 2004.

  1. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    Irvine CA
    Full Name:
    My '76 308 failed the California smog test months ago and since I started screwing around with the carbs and distributors, I can't get it running right. I can't get it to run even as good as it was when it failed the test.

    I've installed new plugs, plug wires and points. Gapped the points to .35 MM and used an ohmmeter and paper template to set the opening and closing of the points at 56 and 34 degrees. The car has single point distributors.

    I haven't replaced the rotors or distributor caps.

    The car is hesitant when driving and is "spitting" (backfiring I guess) through the carbs on the rear bank. Also, when I set the timing, I could see the flywheel marks jumping in and out of the strobe light. "Ghosting" would be a good description of what the timing light is seeing.

    Totally perplexed here. The only thing I can surmise is a bad distributor cap.What else could cause it to miss and "spit" gas out of the carbs? Notice some small cracks in the distributor cap for the rear bank but can find no major damage or signs of arcing inside the cap like traces of soot from arcing from one contact to the other.

    Installing an electronic ignition is an option. But that won't fix arcing inside the distributor cap if that is the problem.
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  3. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    Sounds like the distributor and in particular the throw weights and advancement cam are not properly lubricated. These weights, springs, and cam control the advance per RPM for the engine.
  4. pma1010

    pma1010 F1 Rookie

    Jul 21, 2002
    Full Name:
    You can get spitting up through the carbs if one bank is too lean or if the carbs are not properly sync'd. If you've been through the carbs, I assume you know how to set them up.

    Have you measured the timing at idle for front and rear banks?
  5. Mike328

    Mike328 F1 Rookie
    Rossa Subscribed

    Oct 19, 2002
    Boulder, CO
    Full Name:
    I'll also chime in that there is at least one electronic ignition--the Electromotive HPX--that is distributorless and replaces both your two coils and the distributors (although you can leave the distributors on).

  6. BigTex

    BigTex Seven Time F1 World Champ
    Rossa Subscribed Owner

    Dec 6, 2002
    Houston, Texas
    Full Name:
    Before you really mess up your car, you need to get it somewhere and sync the carbs from square one.

    A cracked distributor cap isn't great news, because they are expensive, but if you need one, you need one.

    Varying timing mark sounds like advance malfunction, and this can only be checked by putting the distributors in machine and fixing them. Can any of you guys close to him point him to a distributor machine?

    I'm so sorry you are not closer. My car having all of the above done since purchase, can be heard for three blocks winding thru the gears!

    You're gonna hurt your car, driving it that way!
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  8. MarkCollins

    MarkCollins F1 Rookie

    Jul 2, 2002
    South England
    Full Name:
    Mark Collins
    Err I know it's pretty basic but are the plug leads in the correct positions on the distributor cap for the rear bank? a couple wrong may cause the symptoms you are seeing
  9. Wayne 962

    Wayne 962 Formula Junior
    Rossa Subscribed

    Nov 27, 2003
    Check the mixture (AFR) at the tailpipe, this will tell you if the carbs are setup properly. There's another thread (308 carb jet) that gives more info...

  10. rufus

    rufus Karting
    Silver Subscribed

    Nov 6, 2003
    Toronto & St PetesFL
    Full Name:
    Pete Gorrell
    To agree with Mark: Ferrari numbers their cylinders in a peculiar way.. twice I've seen problems like yours because the plug leads were wrong. Any chace someone non-F familiar hooked up your leads? Numbering is front to back on right, then back to front on left.
  11. ricrain

    ricrain Karting

    Nov 1, 2003
    Dallas Area
    Full Name:
    1) What kind of wires did you use?
    2) What kind of plugs (resistor or not)?
    3) Do you have resistive extenders or not?
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  13. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    Irvine CA
    Full Name:
    Thanx for all the replies:

    The plugs are OK and the new wires are just 8mm red standard coil core. The extenders are old, not resistor, but functional.

    I think I need to remove the distributors and test the advance weights and lubricate them. That's the first step.

    I have a template I made up for setting the dwell on the distributors. It gets glued to the top of the distributor and allows me to adjust the points to 35mm and open and close on the four 54 and 36 degrees positions.
  14. ricrain

    ricrain Karting

    Nov 1, 2003
    Dallas Area
    Full Name:
    I've repaired more than just a few poorly running 308's just by replacing old extenders (including my own). They may look OK & may read correctly on an ohmmeter, but tend to allow "coronas" when they get old. Drastically different physics are involved at 18KV than at 3V on a meter! Before doing anything else, you're just asking for trouble if you don't replace your extenders.

    Also, if your extenders are not resistive, are your plugs? One or the other has to be, or you've got a major impedence mismatch (which also will cause ghosts on the scope).
  15. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    Irvine CA
    Full Name:
    Extenders probably need replaced. They are old.

    But my problem is the car was running much better before I started my "tune up." If there were problems with the extenders than it would have been apparent before I started the tuning.

    It appears I've finally got the points adjusted properly and the timing set. Just confirmed that this afternoon.

    But the car is still runing poorly and I think it's because my SK Synchrometer is not working properly.

    See the thread: "My SK Synchrometer Appears Broken."
  16. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    Stop and take a deep breath. Don't guess. Before you pull extenders etc.. You need to do proper diagnosistics and go back to basics. Start by being damn sure your static timing is correct and that all wires are going to the right place and all coil terminals are correctly wired. Make sure you fuel system is delivering properly and that the mechanics of the carbs like float levels are correct and jets clean. Then start with the linkages disconnected and the screws closed all the way and backed out to the starting position. These carbs are actually very precise and you should not need to crank screws all over the place to get everything synched. Then reconnect your linkages. You really need a CO meter to properly adjust the carbs after synching. The CO meter will get you to the best point of tune at your current conditions. I.E. if your car runs like sh&t you need to go to the next diagnostic step which is to get an elcheapo meter Like the Italian digiteck 2000 scopemeter to see what your plugs are individually doing. Otherwise you can just change all the parts until you guess correctly. Also, these cars are getting really old. If you have not done so you really need to take the distributors out and have them serviced on a sun distributor machine to set-up the weights even relative to each other and put new distributor bearing in etc... Before you change to non-OEM Ferrari be warned that all these devices work great at first but just do not seem to have the long term OEM toughness and you will fail the smog visual even if you pass the sniff test in some states. So if you are going to modify ignition you may need to hide the mods. For example many gut one distributor and use it as a slave and one distributior as a master with an optical pickup. Smog guys are too dumb to realize. Finally fouled cats can make for very poor running and fail a smog test. When these cars are set-up right they pass smog just fine and I'm in the Nazi republic of kalifornia.

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