I'm Havinng Issues With a 308 3-7-37 Fly Wheel | FerrariChat

I'm Havinng Issues With a 308 3-7-37 Fly Wheel

Discussion in 'Technical Q&A' started by donaldh2o, Sep 28, 2006.

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  1. donaldh2o

    donaldh2o Karting

    Nov 10, 2003
    143
    Irvine CA
    Full Name:
    Don
    #1 donaldh2o, Sep 28, 2006
    I been here before - With the help with chatters awhile back, I was able to get the timing right on my '76 308 with a 3-7-37 fly wheel but now I can't remember.

    I recently had a local shop install new cam belts and the car ran terrible. Then I checked the timing and realized the shop likely assumed it was a 6-16-34 degree fly wheel because when I checked it they had set the timing to 3 degrees, thinking they had set the timing to 6 degrees. Yesterday I moved the timing up from 3 degrees to just past 7 degrees with a substantial improvement. But it's still behaving as if the timing is still too retarded.

    What is the right timing on a 3, 7, 37 fly wheel?

    All along I've assumed the reason for the 3-7-37 fly wheel conversion was because my car was converted to single points distributors rather than R1-R2 dual points. Or could it have been I had different cam shafts installed. Both of these changes took place back in the early 80s.
     
  2. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
    Full Name:
    Kenneth
    #2 Ken, Sep 28, 2006
    Rule of thumb is to advance the static (idle) as much as you can before it pings, or until the car will not start smoothly. On my car it's just shy of 12 degrees and yours should be a little less since you have a lower compression ratio. I bet you can run 8-10 degrees. I'm sure the factory will not have the best full advance listed due to emissions issues; Lotus says my US version should be 6 degrees and the car doesn't run nearly as well as with 12.

    I wouldn't be surprised if your mechanic messed it up, or went with factory spec which in the US is rarely the best state of tune. What about your car's running makes you think it's still too retarded? Bad low end torque?

    Ken
     
  3. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    25,156
    30°30'40" N 97°35'41" W (Texas)
    Full Name:
    Steve Magnusson
    #3 Steve Magnusson, Sep 28, 2006
    If you get the ignition timing sorted out and it still runs poorly, I think you're stuck with the non-trival task of trying to verify the cam timing is OKish (since you just had that messed with).

    The change on the flywheels was/is related to the change in the advance curves between the S159A (as described in the circa 1973 308GT4 WSM) and S159B Marelli distributors (as described in the cat-equipped 150/78 OM) -- both flywheels have three mark and are intended for a system using both R1 and R2 points (one for R1 and R2 active, one for R1 only, and one for total advance at 5K RPM).

    The only caveat that I'd add to Ken's comments is don't let the total high RPM advance get too high if you kick up the 1000 RPM idle advance.
     
  4. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
    Full Name:
    Kenneth
    #4 Ken, Sep 28, 2006
    This is really important; on my car it's not an issue because the OEM distributor is not really matched for the engine. Mine only advances 25 degrees instead of the 38 it could use. But I expect on a Ferrari you can overdo it. Be sure you know what the maximum advance your can can handle and don't go over!

    Ken
     

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