Motor mount condition | FerrariChat

Motor mount condition

Discussion in '308/328' started by 3px19, Jun 25, 2024.

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  1. 3px19

    3px19 Karting

    Aug 29, 2006
    218
    Full Name:
    Calvin crouch
    Pulled my engine this weekend, gt4, and the question is how do you tell a bad motor mount. I gave on that clunks when you shake it but screw in the mounting bolt and it is really secure just like the non clunking. I had an alfa which had good mounts that clunker. Don't want to incur cost of new mount if not needed as they are a chunk of change.
     
  2. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,024
    I've wondered this. Do they sag? I don't hear of too many getting changed, or issues with them. The top mount strut bushings get heat soaked from the rear header, crack and start to look ugly.
     
    Andreas Engesvik likes this.
  3. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,736
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    Sadly I think the answer is that like everything else made of rubber at 10 years they are past their prime, by 20 they are sad and by 40 they are dangerous. 308 mounts (and I assume gt4 mounts) have springs and rubber and the springs hold up really well so its pretty near impossible to tell when the rubber has failed but the rubber is their to act as a damper so as it fails the engine bounces more and more.....but I'm unclear about what issue that could/does cause exactly?....it could lead to broken springs in the mount I guess?
     
    BenB and Andreas Engesvik like this.
  4. smg2

    smg2 F1 World Champ
    Sponsor

    Apr 1, 2004
    16,329
    Dumpster Fire #31
    Full Name:
    SMG
    All the ones I've taken apart the rubber is simply a dust/debris cover. The internal is a tuned spring with a metal mesh damper. So the big killer is rust. The rubber doesn't play a role that I've seen other then to keep it clean.
    They're tuned isolation dampers, so spring condition is critical.
     
    2dinos and waymar like this.
  5. mk e

    mk e F1 World Champ

    Oct 31, 2003
    13,736
    The twilight zone
    Full Name:
    Help me get this thing finished! https://gofund.me/39def36c
    [QUOTE="smg2, post: 149703240, member: The internal is a tuned spring with a metal mesh damper.[/QUOTE]
    Metal mesh damper? My brain just isn't processing that, how does that even work?
     
  6. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,024
    So how would you know they have problem? Can you see rust? Can they be opened without cutting apart? Will engine vibration be more harsh?

    Thanks!!!
     
  7. chrisnmorse

    chrisnmorse Rookie

    Mar 21, 2018
    11
    When I first started tracking my 77 coupe, I experienced difficulty downshifting from third to second at thunder hill, coming up the hill, braking and truning left, then right, (forgot the turn number, been 6 years). I surmised that the mounts were loose, allowing a poor alignment of the chassis, shift linkage and tranny.
    One of our more experienced guys suggested replacing the mounts, with his poly urethane units. Worked like a charm, the chassis/tranny relationship stayed more constant, allowing the shifts to happen much more easily, particularly under braking and turning.
    As with most all hot rod parts, there are tradeoffs, in this case, the stiffer mounts allowed a noticeable increase in engine vibration in the cabin. Not objectionable, but perceptible.

    Looking forward to getting back to T Hill, great track, but first, i need to fine tune my dad's Porsche 911, 2.8 twin plug hot rod and let it rip. Will bring good buddy, for shake out that helped me finish the car. dyno set up first.

    Cheers,
    chris
     
  8. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,024
    That really (to me) sounds like the shift bushing. Coincidentally, mine just acted up last week, and shifting suddenly went 'goofy'. I knew of that little rubber bushing being a common issue, so first chance I got, I looked at it and noticed it was pretty bad. I had a relatively fresh new part, so in 20-30 minutes, all fixed. Took her for a good drive and then changed the oil.

    How we love them so!
     
    Du_Man likes this.
  9. BenB

    BenB Karting

    Dec 14, 2007
    93
    Illinois
    Full Name:
    Ben B
    If you're pulling the engine & the car has its original motor mounts, I can't think of a good reason NOT to install new ones. There's no better time.
     

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