308 Clutch Upgrade - Help Please | FerrariChat
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308 Clutch Upgrade - Help Please

Discussion in '308/328' started by bjmurph, Apr 29, 2016.

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  1. bjmurph

    bjmurph Rookie

    Feb 1, 2011
    11
    #1 bjmurph, Apr 29, 2016
    I am about to undertake the SB21-2 upgrade to my '79 308 GTS. Thinking a bit latterly, rather than replace all the parts that Ferrari specify, I am going to try some alternate ways.

    Specifically I would like to retain the original fork/shaft with the bolt on lever, and to change the length of this lever to suit.

    To this end I need to know the dimension of the upgraded clutch throw out lever (from the C/L of the shaft to the C/L of the bearing) on 81+ 308/328s

    So are there any QV or 328 owners out there who regularly crawl under their cars. If so could you please take a moment to measure the throw-out lever coming out of the bottom of the bell housing and let me know the dimension from the centreline of the vertical shaft to the centreline of the bearing on the end of the lever

    Greatly appreciated
     
  2. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    May 4, 2001
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    #2 Dr Tommy Cosgrove, Apr 29, 2016
    What is your goal?
     
  3. bjmurph

    bjmurph Rookie

    Feb 1, 2011
    11
    #3 bjmurph, May 2, 2016
    Hi, my goal is to reduce the heavy clutch actuation of my '79 GTS. I plan to use my 308 as a weekend pleasure driver, no track work. So am looking to reduce what is for me, a heavy clutch.

    Using SB21-2 as a guide, I tried to purchase the parts only to find that some are not available (not surprising), and after taking some time to peruse the Service Bulletin, the upgraded system appears quite simple, unlike the OE earlier one. I believe that I could effect this upgrade by modifying the length of the original throw-out lever, and then by machining up a suitable bellcrank out of alloy billet. Not only would this be much cheaper that Ferrari parts (almost $1500) but also an interesting project which, of course, I would share.

    Any assistance you can provide would be greatly appreciated.

    Bernie
     
  4. Jet Lag

    Jet Lag Karting

    Dec 6, 2003
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    Seattle
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    Robert Bangs
    #4 Jet Lag, May 2, 2016
    Last edited by a moderator: Sep 7, 2017
    The original '79 308 GTS clutch is not heavy at all if it's set up right.
    Have you checked the clutch cable, or the throw out bearing?

    The clutch cable eventually cuts into the part that goes through the floor and then binds in the 'V'. You can change where the cable rubs by using a spacer, or just install a new cable.

    A worn throw out bearing carrier can make the clutch seem heavy. If the bearing carrier is as worn as the attached picture the bearing will bind causing a heavy clutch. A cheap fix is to turn the carrier 90 degrees and have milled to use a fresh surface (with a new bearing of course). New carriers are a little pricy.

    I'm sure other members have more suggestions for you....
    You can also try squats and lunges.

    Good luck!
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  5. smg2

    smg2 F1 World Champ
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    #5 smg2, May 2, 2016
    The diaphragm requires ~52lbs to release. The pedal effort is ~35lbs.
     
  6. Alden

    Alden F1 Rookie
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    Apr 25, 2010
    3,604
    Central Florida
    #6 Alden, May 2, 2016
    Not sure if this would work on your 308 but you may be able to add a vacuum driven hydraulic booster to the clutch, someone on the forum did that to make the clutch effort on their car more reasonable.

    It was a simple bolt on power brake booster with some hydraulic fittings thrown in and a vacuum line to the engine.

    Try a search, I will too, maybe we can find the thread.
    Alden
     
  7. miketuason

    miketuason F1 World Champ
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    #7 miketuason, May 3, 2016
    Wow! Instead of a power brake, it's a power clutch. Nice!
     
  8. Alden

    Alden F1 Rookie
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    #8 Alden, May 3, 2016
    Yep, and from what the owner said it worked great!

    I think it was on a 348 or 355.....

    (Searching, searching........)
    Alden
     
  9. jessup

    jessup Formula Junior

    Apr 26, 2014
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    Santa Clara CA USA
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    #9 jessup, May 3, 2016
    Many new cars use a return spring on the pedal assembly that goes over center. As you push the pedal past the throw out bearing contact point it helps pull the pedal to the floor.
     
  10. sltillim

    sltillim Formula 3
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    #10 sltillim, May 3, 2016
    There was a hydraulic conversion that people have mentioned on here before.
     
  11. smg2

    smg2 F1 World Champ
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    #11 smg2, May 3, 2016
    umm guys, the 308/328 uses a cable for the clutch actuation. Purely mechanical and relying on leverage,but even with the Mondials hydrolic setup the force was the same. ~35lbs to operate.
     
  12. sltillim

    sltillim Formula 3
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    #12 sltillim, May 3, 2016
  13. bjmurph

    bjmurph Rookie

    Feb 1, 2011
    11
    #13 bjmurph, May 3, 2016
    Thanks JetLag. My throw-out bush is fine; no indentations & the bearing is good (though I'll replace it). I have also checked the cable and while a little dry; is clean & straight with no broken strands.

    What I have found is that all the bearings on the cross shaft (my car is RHD) though feeling OK when I first removed the shaft have been found to be dry & crunchy on further inspection. This is an easy fix as the parts are available at your local bearing store for $A30.

    I suspect that the main changes in SB21-2 are the movement of the pedal return spring from adding to clutch effort to reducing that effort. I also suspect that the ratio of the throw-out lever & bell-crank on the bell housing are different to reduce effort. I wonder however whether reduced effort means longer travel?

    I'm now thinking of buying a 2nd hand bell housing from a QV and transferring parts, but would still like to know the dimensions of the QV/328 throw-out lever & bell-crank to see what I'm getting.

    Anyone out there who can help me with this?

    A further question: has anyone actually performed the SB21-2 upgrade?
     
  14. Alden

    Alden F1 Rookie
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    #14 Alden, May 4, 2016
    From that thread:
    "The earlier models had very hard functioning clutch pedals, especially neutral to first. So hard that the geometry of the linkages/cables were changed for the Japanese market cars (conclude what you want from that). Anyway, back around 1999 or 2000 IIR Forza published a "How To" article with this linkage change, as I recall you can do it in your garage and it made a big difference. You may find the article on here if you search, I believe it was posted."

    So, Ferrari changed the geometry to make it easier. Is that the "SB21-2 upgrade" you are talking about or do we need to find that issue of Forza?
    Alden
     

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