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Tech: Engine Mount Solidification

Discussion in 'General Tech Articles' started by Vexamus, May 20, 2003.

  1. Vexamus

    Vexamus Member

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    Sup? Here's a quick lesson into how and why you'd want to solidify your motor mounts.

    Let's start with a little bit of theory.

    Back in the day, engines were just bolted to the frame rails of the cars making for very little inter-chassis movement(engine moving inside the car). This was ok, becuase with a V8, the power hits every 45 degrees alone the axis so the vibration is distributed pretty evenly over a circle.

    However in I4 configurations, the power hits every 90 degress of the crank turn and it's momentum sometimes is transferred forward or backward depending upon where in the cycle, each cylinder is. This is why they came up with rubber engine mounts, that look something like this:

    [​IMG]

    This flexibility makes it so that the harsh vibrations that 4cyl engines create don't transfer into the frame rails, and in turn into the cabin, making for a very quiet ride.

    Above you see what we in the 4 banger world would call a "front" mount, when in actuality it's a side mount. (front of the engine is the accessories side. Think V8). This front mount is also called a Torque mount, and aside from the primary function of holding that part of the engine up, it's secondary purpose is to allow the engine to move when you nail the throttle. This actually eats up torque and keeps it from getting to the wheels prohibiting burnouts or breaking the tires loose as easily. This is done in regulary consumer vehicles for stability, and quietness.

    Here you see the rear mount(another side mount in actuallity).

    [​IMG]

    You can see the extra space put into the mount, but not nearly as much as the front mount, this mount is designed to absorb the jolts of shifting the manual transmission. The mount for the AT Accord and most AT cars are different for each respective vehicle.

    These two mounts are crucial in the control of interchassis movement. To make a car ride easier and quieter, soften these up. For racecar applications where you need the most torque and horsepower to reach the wheels, you make them solid. Making them solid is a big choice because once you've done this there's no going back without a lot of work.

    The Process

    In the above two pictures you'll see that I have my front and rear mounts out(I'm only doing these two because these are the two that control engine movement.).

    When taking these two out, be sure of two things... firstly, that the car is supported properly, and secondly, and most importantly, that the engine be supported because the transmission mount will collapse over time if left with the roughly 550lbs of cast aluminum resting on it. There's no practical reason to solidify this mount unless you just need any lateral noise to transfer into the cabin.

    This process of solidifying can and will sufficienly repair any cracks or broken urethane on the stock mount so long as the position of the steel tube hasn't changed due to the break.


    Inventory
    • 80A Urethane Casting Compound and activator
      [​IMG]
    • The mounts out of your car(see above)
    • Someplace out of the weather and at room temperature.
    • Lots and lots and lots(I'm not kidding here) clorox wipes, it's the only thing that will break it down if you get it on ANYTHING.
    • One tube Maternal nipple cream.
      [​IMG]
    • One box prescription STOOL SOFTENER.
      [​IMG]
    FYI, the last two items are a joke, I just used them to prop the mount level. :)
    Steps
    1. After removing the mounts, wash them thoroughly with warm water and simple green as seen here in these two photos: [​IMG]

      [​IMG]
      They should be washed so that when wet with water, you can't get any more debris on your finger when you run your finger throughout the rubber area. This is essential for proper bonding of the Casting compound.
    2. Next, dry the mounts thuroughly using a hair drying or just laying them on your heater/cooler vents or outside for a while if you're not in a hurry. They have to be 100% dry, don't assume, make sure. Water is the enemy of Urethane.
    3. When the mounts are all dry, the best thing to use is Duct tape to seal at least one side of them. You're going to be pouring a very runny liquid into the mounts, and you HAVE to get a good seal, if you look closely at the pictures, you'll note that on the rear mount, I didn't have a good seal.
      [​IMG]
      [​IMG]
      It's really going to be up to you as your mounts may be different.
    4. Mix and pour in your casting compound according to the directions that came with it. If you buy liquid compound by the lbs, it will come in a pre measured kit where, in my case, I just mix the base with the activator and I'm done. If it didn't come premeasured either consider buying a kit or read your instructions very carefully, the Urethane undergoes an exothermic reaction and if there's too much of one thing it can ruin the whole batch(i.e. swiss cheese).
    5. If you're like me, you're going to have to baby sit it and keep adding more. 1lbs of casting compound would normally fill 4 or so mounts, however, because my rear mount kept leaking I kept adding some more and more and finally, I got tired of doing that(read: I ran out of compound) and had a friend gob more tape on the mount, finally sealing it in place. If this is your first time and/or you're like me and not very good with tape expect this:
      [​IMG]

      Luckily, I didn't get any on the stove it managed to stay on the box.
    6. Keep in mind, you have 15 minutes or so to work with this stuff after you mix it, so pour quickly. it should get tacky in that amount of time and may act like cheese if you try to move it(i.e. split instead of spread). Once set after a few hours, you can remove the tape.
    7. After removing the tape, inspect the casting for cracks and bubbles, indications that the mixture was improper. If all goes well, you should have something that looks like this:

      [​IMG]

      [​IMG]
      The tape made the imprint, the tape is actually removed.

    8. Let sit at room temperature and dry for at least 48 hours after removing the tape to ensure that it cures properly before you put any weight on it.
    9. As gay as the term is: The installation is the same as removal. :)
      [/list=1]



      Good luck!!!

      --Vex
     
  2. pissedoffsol

    pissedoffsol RETIRED

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    good post :)
     
  3. Vexamus

    Vexamus Member

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    Thank you.


    As an update, I find this mixture of 80A to be sufficient for ZERO engine movement but it doesn't transfer every little clink into the chassis, it's quite nice and solid.. Makes the motor sound more like a race car both inside and outside of the car.
     
  4. KyleCrews

    KyleCrews Senior Member

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    Great post. You can also use a tube of polyurethane that you can geat from Napa or some other parts store if you don't want to go don't want to go through the hassel of mixing and trying to get it right. Used it on my mounts, took about 2 days to fully cure. Works great. I now have virtually no engine movement at all and the idle isn't too ruff in the car.
     
  5. Loco Honkey

    Loco Honkey Banned

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    Let me correct some mistakes by saying that a V8 produces power pulses every 90° and an I4 has a pulse every 180°. And installation is NOT the same as removal. It's opposite.

    Otherwise, good writeup.
     
  6. JDMilan

    JDMilan Senior Member

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    Loco you punk,,,LOL


    good write up, thumbsup



    Milan
     
  7. evoracer03

    evoracer03 Senior Member

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    some of the best suff ive found is called window weld from 3m i believe. its the same stuff they use to put your windshield in and you just put it in a caulking gun and squeeze it in the mount, takes about three days to dry fully though. but then the mount is nice and solid ive got about 25000 miles and 15 race weekends on them without a problem on 88 dx w/ z6 swap
     
  8. Vexamus

    Vexamus Member

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    Ah, that's the testimonial I was looking for. Based on that, I won't be so negative on the window weld method... thanks.

    And loco.... DAMMIT!! I was gonna argue...

    I just look at it thermodynamically, and that's why I get the numbers I do... but yes, you're right and in the context that I presented it, I was incorrect.... lol Nice..

    And installtion IS the SAME as removal..... I'll argue that one for no reason... lol

    thanks for the props everyone.
     
  9. highperboi

    highperboi Senior Member

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    where do you buy that stuff?
     
  10. highperboi

    highperboi Senior Member

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    wth i got that 3m stuff and i put it in and its been 2 days and its not dried one bit reall. under the tape its still freaking wet as heck. how do i dry them? i tried heat gun and it didnt really work it just melted it. help anyone?
     
  11. xj0hnx

    xj0hnx I wanna be sedated VIP

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    Ho would this work on trailing arm bushings?
     
  12. eml1618

    eml1618 Member

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    Works like a charm, thx :worthy:
     
  13. Loco Honkey

    Loco Honkey Banned

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    Ya ain't gonna win this one, buckshot...

    Installation is indeed opposite of removal. Let's say you're adjusting your valves. 1st step is to remove the plug wires. 2nd step is to remove the valve cover. Ect..

    Upon putting it back together, it is impossible to remove the plug wires as they are already removed. However, let's say that upon putting it back together, you were to reinstall the plug wires. This is still impossible, because you have to install the valve cover first, which, in othe order of removal, was step two, however in the order of reinstallation, it is the 2nd to last step, therefore, proving beyond a shadow of a doubt that indeed, installation IS opposite of removal.
     
  14. weirdman77

    weirdman77 Junior Member

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    i was wondering

    what do you gain from this mod
     
  15. Jhonda

    Jhonda Member

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    hmm bunch of idiots complaining about a guy who takes the time to put up his idea and u guys wanna bitch because h missaid one thing ,and window weld come on sounds like somthin a hick would use on his ford or dodge ..in my opinion great article .so shut the @#$% up
     
  16. NoJokE

    NoJokE Senior Member

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    The engine doesnt move as much in the bay when accelerated putting more horsepower to the wheels.

    There will be more vibration in the car however. Little things like cupholders and such.
     
  17. Canuck 93 Civic Si

    Canuck 93 Civic Si Senior Member

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    Ya where can i pick some up?
     
  18. cointelpro

    cointelpro Senior Member

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    is the added vibration in the car very noticable? because i would love to do this when i do my swap but i dont wanna be sitting in a massaging car, ya know what i mean?
     
  19. Vexamus

    Vexamus Member

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    Ok, real quick.

    I was corrected, admited to being incorrect and then made a joke and somebody thought I was serious... aight...

    Anyway,

    Solidifying your mounts does increase vibration, but also minimizes if not eliminates all movement of the engine relative to the car, this will eliminate wheel hop if you burn out. Secondly, it's easier on your drivetrain because your motor won't bounce when you shift.

    Lastly, if you have a nice tight frame in your car, the sound resonates through the frame and makes it a much deeper sound, just an asthetic thing, but yeah, that's how that works.

    Any more questions, feel free to PM or reply here.
     
  20. Sobe_Death

    Sobe_Death Senior Member

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    why not? all the muscles in your back and legs would be completely stress free!!
     

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