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dialing in carbs

Discussion in '308/328' started by decardona, Mar 8, 2010.

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  1. decardona

    decardona Formula 3

    Apr 23, 2005
    1,019
    PA
    Full Name:
    Dennis Cardona
    #1 decardona, Mar 8, 2010
    I just finished putting in a pertronix ignition system in myy 77 308. Got the timing spot on. Now it runs a bit rich. Popping and a bit of backfiring. My question is, how lean is too lean and what kind of damage can be caused by running too lean. My setup is very close. Can go all the way to redline thru first three gears, but get some popping at about 4500rpm in 4th and 5th. Then once the popping starts, it seems to continue until I can get back to a steady speed. Any advice?
     
  2. bwassam

    bwassam Formula Junior

    Jan 3, 2005
    635
    North Bend, Oregon
    Full Name:
    Robert Wassam
    #2 bwassam, Mar 8, 2010
    Last edited: Mar 8, 2010
    Check the floats. They may need to be raised a little bit.

    I have a '77 to and was experiencing the same problems. I was told to check the floats because the new gasoline with ethanol doesn't produce as much bang. So you may be needing a bit more fuel. Also if you popping is through the carbs, then you may be running a bit lean already at the top end. If it ran good before, you may want to check the timing again. Move it a degree retard or advance. I think you can change it with the computer. The advance may be a little different from the point system that you replaced. Tell me about installing the pertronix system. I'm thinking that I would like to do it to my car too.

    I've got so many things to do to my car to get it close to running like I want that it's hard to decide what to do first.

    OH yeah, the worse case senario for running real lean is the loss of a valve. If you decide to replace your valves I suggest that you go with stainless steel valves from Nick Forza's Ferrari. He's got a good web site.

    Bob Wassam
     
  3. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,030
    #3 2dinos, Mar 8, 2010
    I hate to look in the direction of your freshly installed ignition system, but popping (IMHO) sounds like a spark problem. Two distrib setup? If so, the phasing, cross talk across wires, crack in a cap, bad plug extender(s). The popping is consistent as a function of RPM regardless of load? How did it run before you put in the new ignition?
     
  4. decardona

    decardona Formula 3

    Apr 23, 2005
    1,019
    PA
    Full Name:
    Dennis Cardona
    #4 decardona, Mar 9, 2010
    Everything is new and checked before install, (caps, wires, extenders, plugs). It is a two distributor system and it ran well on the old points system. Only problem was at top end, at about 6000rpm, it became hesitant. It would push thru, but it took awhile.
     
  5. decardona

    decardona Formula 3

    Apr 23, 2005
    1,019
    PA
    Full Name:
    Dennis Cardona
    #5 decardona, Mar 9, 2010
    Thanks for the info on the floats, I will check it out. I will also relook at the timing. I have a local station that has no ethanol gas, so I don't think that is the problem. If you search, you will see most people go with the single distributor pertronix setup. It has to be modified to work. I went with the dual distributor setup that was designed with the help of a fellow f-chatter. It installed very simply. Took about a full afternoon to complete. Directions are very easy to follow.
     
  6. decardona

    decardona Formula 3

    Apr 23, 2005
    1,019
    PA
    Full Name:
    Dennis Cardona
    #6 decardona, Mar 9, 2010
    Got home from work today and went to work on the car with the above advice. After rechecking and readjusting the timing, the car is great! Runs smooth thru all gears to redline. Didn't get to try that in 5th, but when will I. Clean, hard accelaration. Great reaction when downshifting with throttle up. Only popping is when shutting down, but it is more of a gurgle than a pop. More than acceptable. Thanks to all those, thru several threads, that have provide info and advice.
     

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