Motor mounts or shift linkage? | FerrariChat

Motor mounts or shift linkage?

Discussion in '308/328' started by jsa330, Jun 16, 2011.

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  1. jsa330

    jsa330 F1 World Champ
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    On engaging the clutch after a fast high-RPM second-third upshift, the shifter handle in my '83 308 GTS twists quite noticeably to the left.

    Suspects are deteriorated motor mounts or worn/out of adjustment shift linkage components. I've done a search and found lots of discussion on these but no conclusive answers.

    Knowledgeable insights greatly appreciated!
     
  2. pad

    pad Formula 3

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    To answer your question, I think you need to check both areas. The engine torques clockwise when it is revved (when viewed from the front pulley). In the case of the 308, that means the engine will torque towards the front of the car and not sideways as in a conventional front engined car. Based on that you have stated, I would look at several things.

    First, look at the engine mounts. A bad engine mount will allow the engine to move side to side while torqueing front to back as it would when you engage the clutch after a "getting it on" shift. Next, check the shift linkage bushings. If the bushings and/or engine mounts are old, they are probably due to be changed.

    And while you are at it, check the top engine reaction tie bushings and shim adjustments. If you remove one of the reaction tie bushing through bolts and the engine moves, you know you have a suspect engine mount(s). Again, if the rubber bushings (called link buffers) are old, they too will probably need replacing.

    Again, based on that you wrote, I would not suspect the actual shift linkage adjuster (the turnbuckle on the external shift rod) being loose. If so,you would be experiencing all types of shifting issues.

    One more thing, after you replace the various bushings and mount(s), you will possibly need to readjust the shift linkage. Just one more step in the process of getting things right.

    Good hunting.
     
  3. jsa330

    jsa330 F1 World Champ
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    Paul...thanks; knowledgeable answers indeed and most helpful.

    Is replacing the mounts an engine-out job?
     
  4. BigTex

    BigTex Seven Time F1 World Champ
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    I would not think so, I have unbolted them at the bottom, to lift my engine slightly when changing headers.

    There's a thread about some from Summit Racing that can be slightly modifed to fit.

    The SOLID mounting does give you a slight increase in vibration thru the frame....:D :D :D

    There was also a chatter in Europe that had some usable take offs for sale CHEAP...I'll try to recall...
     
  5. BigTex

    BigTex Seven Time F1 World Champ
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    Make sure you note where the shims are, under each one..
     
  6. jsa330

    jsa330 F1 World Champ
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    Thanks for the good advice, Bubba.

    Norwoods will do the work if they need replacing...maybe I'll blow it all out and have the engine pulled, get some Nick's Forza mods done, and clean up/detail the engine and compartment before it goes back in.

    If you do come across a source for less expensive mounts, by all means let me know. Four @$274.45 each from Ricambi = Ouch!

    I'll check out the Summit Racing thread.
     
  7. pad

    pad Formula 3

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    To change motor mount, disconnect shift linkage by engine, remove top reaction tie bar, place floor jack w/ wide board under engine, unbolt engine mounts from frame member (1 bolt per mount), lift engine slightly, unbolt engine mount frames from engine (4 bolts per mount) keeping track of shims and washers and their orientation, insert new mount into mount frame, then reverse the procedure to install. I don't think I forgot anything.....

    Of course, if you pull the engine, the changing of the mounts is a piece of cake....
     
  8. viper_driver

    viper_driver Formula Junior

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  9. jsa330

    jsa330 F1 World Champ
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    I previously looked on SP's website but didn't find them...guess I didn't look hard enough. Thanks for pointing them out.

    I've bought stuff from them before...they're a good outfit.
     
  10. Brian Harper

    Brian Harper F1 Rookie
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    Under acceleration load the engine should rotate counter-clockwise as viewed from the front of the engine. The crank has some rotational force, but if that isn't completely swamped by the output of the drive axles trying to lift the front of the car, it is time for a tune-up. The engine is trying to turn the wheels clockwise, the equal and opposite reaction is counter-clockwise.

    At this point in automotive history I'm afraid that a sideways motor up front is conventional. We don't have to like it, but transverse front wheel drive rules the road by sheer numbers.
     
  11. pad

    pad Formula 3

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    Brian, I stand corrected on the engine torque. (I originally wrote counter-clockwise but changed it before I hit the post button. I was recalling when a person I know in college mounted a V8 in a motorcycle frame and I just could not remember which way the bike fell over when he hit the throttle - hell, that was 40 years ago).
     
  12. Brian Harper

    Brian Harper F1 Rookie
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    Yes the engine does torque opposite the crankshaft direction when accelerated freely. I have a Moto Guzzi, I know about that. But the reaction that matters is when the engine is pushing the car/bike. In a front engine/rear drive car this action is turned 90* at the differential so the engine is trying the lift the front of the car and the opposite reaction (turned 90*) tries to twist the motor to the side.

    Why the Boss Hoss bikes don't just fall over when revved hard, I don't know. Make sure you have both feet down!
     

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