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Harmonic balancer rubbing on cross member

Discussion in 'The Garage' started by spoolnaround, Feb 24, 2005.

  1. spoolnaround

    spoolnaround 1/2 ton status

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    Anyone else have this problem? I have replaced the drivers motor mount, passengers looks ok. Its as if the motor mounts have collapsed. With any little torque on the motor my harmonic balancer rubs the cross member and my fan hits the shroud. I am debating on buying a new passenger mount or just getting a set of ORD's comptition mounts. I would hate to spend $160 on the competition mounts if its something else. This is the 5th 73-80 K5/K10 I have owned and never run into this. Am I missing something here? I did change from a 203 to a 205, I cant remember If I had this problem witht the 203 in it or If I even ever ran it with the 203, still that shouldnt have any bearing on T/C height as they use the same cross member anyway. Im lost on this and its getting worse. Any suggestions?
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    I would say it's likely your motor mounts, assuming:

    1. Fan shroud is installed correctly and tight

    2. Tranny crossmember is securely fastened to your frame without any kind of lowering hack jobs or anything like that.

    If both of those are true, I'd say it's your motor mounts.

    The competition motor mounts won't locate your engine any better than regular rubber ones that are new and tight, just so you know.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    I'd bet money that the towers that the motor mounts bolt to are broken.

    My dads '74 had this exact problem (balancer scraping x-member), I believe the setup was pretty well re-designed later by GM, just like the engine crossmember cracking problem.

    I think all the rubber in the mounts would have to fall out before the motor would hit like it does when the metal flexes. I know we found the cause when we went to swap in a 454, I'm not sure you can see the cracks with the engine in place.
     
  4. spoolnaround

    spoolnaround 1/2 ton status

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    I will have to take a closer look, when I was down there I didnt think of looking for cracks. And its a 74 too :(


    Thats what I was thinking.
     
  5. diesel4me

    diesel4me 1 ton status Premium Member

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    check the plates on the motor

    Did you swap this motor in??--if so,the plates that bolt to the engine block may be the passenger car versions that have the thru bolt hole an inch closer to the block than the 4x4 truck ones--I've seen a lot of GM trucks people put car motors in them without swapping the mounting plates from the original motor back onto the replacement motor,it makes the motor point down in the front too much..--it sometimes works ok for awhile,but the balancer can rub once the motor mount sag a little--I've seen one truck that way ,it had the fuel pump resting right on the crossmember!...this might be your whole problem,maybe not...:dunno:
     
  6. mr_beer

    mr_beer 1/2 ton status

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    I had the same problem one time. I changed both motor mounts and it fixed the problem.
     
  7. sweetk30

    sweetk30 professional hooker Premium Member

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    any body check to see if the balencer is bad and walking off the hub piece ?
     
  8. R72K5

    R72K5 Banned

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    wow ive never hear of this one before, lol

    but yeah car mount block brackets are taller for trucks than cars

    good l;uck
     
  9. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    What year is the truck your working on. Your Profile says '74? If that's the case, then you have the little known 73-74 problem.
    Most 73 and only early '74's had different (lower) mounting pads, and then the engine mounts are different (thicker/higher) and specific for those years. No one makes those mounts anymore. Putting in standard engine mounts for the v8 engines will cause a slight rub of the balancer on the front crossmember.
    The solution is to space up the engine mounts. I welded a piece of 1/8" plate to my pads, drilled and painted, then installed the standard engine mounts., that did the job.
    I did the fix but years ago, but couldn't figure out why it ever happened to begin with. Then I read an article in late 90's mag that had a blurb about the problem on the '73-74 trucks.
     

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