torque straps and motor mounts

Discussion in 'MISC. mods and equip.' started by grumpyvette, Dec 14, 2009.

  1. grumpyvette

    grumpyvette Administrator Staff Member

    once your engines hp and torque levels start to significantly exceed the factory levels its not at all uncommon for the engines twisting movement in the frame to start stressing the factory motor mounts, this can result in difficult shifts due to linkage geometry changes or jammed throttles etc.
    On the motor mounts, the driver side is under extension or stretching and the passenger is under compression, as the engine torque increases with shifts etc. so the load is on the driver side. This is the reason for the solid driver mount most guys use is to limit engine movement,. As far as the trans goes, I like having something to absorb any vibes in the car so Ive generally used the hard plastic/ or POLY trans mounts. The weaker part is the aluminum trans case
    many guys go to the stronger aftermarket poly motor mounts or add a short section of chain from the drivers side cylinder head to the drivers side frame to limit the shock loads on the motor mounts that speed shifts, high stall speed converters, higher rear gears and slicks, and much higher torque loads impart to the factory mounts, the first time you bust an engine mount and the throttle jams wide open , you might see the advantages
    many guys simply bolt a short section of chain or an adjustable strap with heim joint ends,between the left side car frame and some solid location like a bolt on the the left engine cylinder head that has just a bit of slack so as the engine torque increases stress on the motor mounts it tightens up as the distance between the left cylinder head and frame increases and significantly reduces the load on the motor mount.

    ALWAYS run a good separate electrical ground strap between the engine and frame , transmission and motor mounts are notoriously bad electrical ground connections to the frame.

    POLY MOTOR MOUNTS and a decent grade 8 set of mount bolts, with loc-tite on the threads will help , check the bolt length, diameter and thread pitch carefully.
    3/8 mount to block and or -7/16" bolt about 3.5" long is the common solution,to broken stock motor mount in a high stress application,
    btw on some motor mounts the bolt holes either don,t line up exactly or the holes a bit under sized so a bit of drill bit time might be required to get the thru bolt to clear easily, so don,t get crazy, test fit the bolt before you install the mounts

    when planing on fabricating a large bracket like that engine mount plate its frequently a good idea to buy , cut and test fit
    a pattern made from dirt cheap clear plastic before starting on rather expensive steel or aluminum, to get all the necessary mods and clearances worked out, the huge advantage of clear plastic is you can easily see where you need bolt holes or some item that moves during operation (like suspension) or more easily let you recognize early in the fabrication process that theres always a compromise some place to be considered, parts like STARTERS , OIL FILTERS AND HEADERS that might become nearly impossible to work on if the brackets in place
    if youve built a real torque monster solid mid plate mounts might be a good idea ... s/CEE-4031

    [​IMG] ... 602&page=1
    IF your having trouble getting motor mounts to line up correctly ,you do realize that chevy motor mounts come in several styles and heights
    1- 11/16"
    1- 3/4"
    2 -1/8"
    2- 3/8"
    2 -9/32"

    theres also spacers for motor mounts
    Part # Description
    62535 Motor Mount Shim Kit

    1/16", 1/8", and 3/16" thick, 2 ea.
    Standard Chevrolet bolt pattern
    Works great with Chevy Motor Mounts 62500, 62510, 62515, & 62530
    Used to make slight adjustments to engine height to compensate for minor oil pan, linkage, and header interference
    Great addition to engine swap kits
    Part # Description
    [​IMG] ...
    theres far more than just these designs





    viewtopic.php?f=38&t=200&p=235&hilit=engine+mounts#p235 ... -Kits.html ... or_mounts/ ... system.htm ... 20U-Joints ... ndex4.html ... Code=11025
    [​IMG] ... index.html


    while hardly high tech,
    adding a simple length of 3/8" chain from the drivers side frame to a bolt in the drivers side cylinder head will prevent a great deal of torque damage to motor mounts

    and yes a commercial version looks better but its not significantly more effective
    [​IMG] ... Code=10029

    if you want to get fancy and do a really nice job you can fabricate custom, adjustable length torque straps with HEIM joint swivel ends,and heavy wall stainless or chrome moly steel tubing and weld a lower bracket to the frame
    [​IMG] ... _info.html
    Last edited by a moderator: Oct 13, 2017
  2. 87vette81big

    87vette81big Guest

    I spent some time researching today Grumpy.
    Solid Motor Mounts . For a C4 Corvette.
    I started with your site of course.
    I found ZERO RESULTS.
    Seems there were 2 different factory engine mounts used.
    Clam Shell style.
    1984-91. Gen 1 Crossfire & TPI & Early 1990-'91 LT5 ZR-1.
    Then the Gen 1 sbc LT1 & LT-4. 1992-96.

    Also Googled searched.
    Read the Corvette based forums & posts.
    It appears none have ever used solid motor mounts in a C4 Vette.
    C4 motor mounts have thier own aftermarket replacement #.
    Does not interchange with Camaro or others
    MOROSO don't show a listing for solid motor mounts in a C4 .
  3. 87vette81big

    87vette81big Guest

    Solid motor mounts are a must in the Drag Racing World.
    Or engine Front & Midplate.

    I can see why C4 's are not considered fast by most....
    Crap aftermarket support.
    No Race Items .

    Had fun reading your old BBC Swap posts & threads.
  4. grumpyvette

    grumpyvette Administrator Staff Member

    the C4 corvette, looks really nice when properly set up, but they are heavy and not easy to work on,due to less than ideal room, to work, plus the rear independent suspension and differential is weak enough to cause problems
  5. 87vette81big

    87vette81big Guest

    Not givng up Grumpy.
    Just means more fabrication required.
  6. chromebumpers

    chromebumpers solid fixture here in the forum Staff Member

    I know a little about how it feels with a throttle linkage stuck in wide open position going down an off ramp into merging traffic! I'll be fastening down the drivers' side on my GTO build for sure!
  7. philly

    philly solid fixture here in the forum

    the adjustable heim joint setup llooks clean, you think it would be overkill or uneccessary to put them on both sides of the motor? just looking at it from a uniform / symmetrical standpoit
  8. 87vette81big

    87vette81big Guest

    If the Heim or Aurora joint is too small it can still break or fail.
  9. philly

    philly solid fixture here in the forum

    do they have some sort of stress ratings? like tensile strengths?
  10. 87vette81big

    87vette81big Guest

    Yes they do Phil.
    Aurora brand Rod Ends have tensile ratings in PSI.
    I used to have one of thier catalogs .
    The Chromoly have the highest ratings.
  11. philly

    philly solid fixture here in the forum

    sweet, i'll lok into it as the project unfolds
  12. 87vette81big

    87vette81big Guest

    Aurora Brand Rod Ends are regarded as the Very Best in the Drag Racing World Phil.
    I do believe all rod ends made by them are 4130 & 4140 construction.

    Aurora rod ends were included in my Competition Engineering Pro Magnum 4-Link Kit.
  13. Strictly Attitude

    Strictly Attitude solid fixture here in the forum

    good reading in contemplation of what mounting system I plan to use with new engine

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