308 gts carb linkage. | FerrariChat
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308 gts carb linkage.

Discussion in '308/328' started by bl10, Feb 10, 2022.

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  1. bl10

    bl10 Formula Junior

    Jun 8, 2011
    442
    Chatsworth, CA
    Full Name:
    Barry Leavengood
    #1 bl10, Feb 10, 2022
    While finally getting my GTS with Pertronix (no ignition retard at idle) to idle at 975 rpm I noticed this lever on the linkage. Any ideas what it's for. I bought the car when it was 2 years old and as far as I know this lever has never connected to anything. Note there is a adjusting screw at the bottom.

    Thanks

    Barry

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  2. 308ROB

    308ROB Formula Junior
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    Aug 14, 2004
    884
    Netherlands
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    Rob
    #2 308ROB, Feb 10, 2022
  3. bl10

    bl10 Formula Junior

    Jun 8, 2011
    442
    Chatsworth, CA
    Full Name:
    Barry Leavengood
    #3 bl10, Feb 10, 2022
    Thanks
    Someone must have removed it for some reason before I purchased it. What is its purpose, simply to slow down return to idle or is it actually a a solenoid to increase idle when the AC is on. Some US cars I'm familiar with used a solenoid device that as I recall looked like a dashpot to increase the idle due to the AC compressor load. I assume since you called it a dashpot there is no vacuum or electrical to it. Is it detailed in any of the schematics? I looked yesterday and didn't find anything.

    I only ask due to the load the AC compressor (York) puts on the engine. I now have it idling great at 975 rpm with AC off and 925 with AC on.. Its fine both ways but its to bad I have to adjust for the AC.

    Barry
     
  4. thorn

    thorn F1 Rookie
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    Aug 7, 2012
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    #4 thorn, Feb 10, 2022
    Though my knowledge of carb cars is rather limited, that's my understand of the purpose - that it's basically a shock absorber for the throttle plate, to keep it from shutting too quickly.
     
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  5. bl10

    bl10 Formula Junior

    Jun 8, 2011
    442
    Chatsworth, CA
    Full Name:
    Barry Leavengood
    #5 bl10, Feb 11, 2022
    Thorn
    Yep. That's what it looks like. Oh well. Still thinking about putting a solenoid there to prop up the idle a little when the AC is on. Another project for another day.
     
  6. ProvaMo

    ProvaMo Formula Junior

    Jun 29, 2004
    351
    Mid West
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    Paul John
    #6 ProvaMo, Feb 11, 2022
    I recall from my muscle car tuning days that some engines were sensitive and would stall if the throttle closed abruptly, hence a dashpot to dampen closure velocity. This link says the same, along with: "This movement allows the vehicle to return to idle smoothly and prevents the emission of high levels of carbon monoxide." I didn't know about the emissions benefit, that's interesting and (slightly) counterintuitive, but I guess if the engine does stall, that could release a bunch of CO, along with a potential safety issue.
     
  7. bl10

    bl10 Formula Junior

    Jun 8, 2011
    442
    Chatsworth, CA
    Full Name:
    Barry Leavengood
    #7 bl10, Feb 11, 2022
    PovaMo
    Your probably correct about the emissions. If the throttle blades snap shut there could very possibility be a anomalous increase in emissions. Having said that mine has never had the dashpot, its a 78 that I bought in 80, and never failed emissions. If anything it seems slow to return to idle and therefore never tries to stall. Even with the AC on with the idle set to 940 (975 with AC off) it never stalls.

    Barry
     

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