Body Flex

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    Author Topic: Body Flex  (Read 6505 times)

    Offline XBRIT

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    Body Flex
    « on: October 12, 2012 - 04:23:58 PM »
    It’s been a three year period after paint and my 72 E-Body has developed a crack in the paint at the body join roof to rear quarter panel.
    This was originally a 318ci vinyl top vehicle and the paint guy is questioning the motor I have now in the Challenger is too powerful allowing the body to flex and cracking the body joint in turn cracking the paint. It is running a 383ci 4 speed. He also said it could have been jacked up on that quarter twisting the body. I told him in 1970 they had a Hemi on the list of options, so my motor is not over stressing the body.
    Did they ever address this roof weld with different engine options?
    Cheers.
    Xbrit

     
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    Offline burdar

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    Re: Body Flex
    « Reply #1 on: October 12, 2012 - 04:56:34 PM »
    What was used at the roof/quarter joint?  Body filler or lead?
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    Offline mojavered

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    Re: Body Flex
    « Reply #2 on: October 12, 2012 - 05:25:43 PM »
    Mine has done the same thing. 
    Do you have torque boxes added?  Subframe connectors added?  Regardless of what engines were optioned, subframe connectors are probably necessary
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    Jason

    Offline moparmaniac59

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    Re: Body Flex
    « Reply #3 on: October 12, 2012 - 05:31:44 PM »
    I have been told by Mopar fans of days gone past that the Hemi's were known for cracking paint along the body lines you described on "E" bodies due to the massive torque and body flex. I've even heard some rumors go so far as telling of some hemi's that even cracked the back glass due to torque & body flex.  :22yikes:



                                                                                 Matt B.
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    Matt

    Offline XBRIT

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    Re: Body Flex
    « Reply #4 on: October 12, 2012 - 05:51:35 PM »
    Hi Guys,
    Factory construction no sub frame connectors and filler not lead.
    It looked to me as though moisture had got under the body filler and cracked the paint.
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    Offline 72bluNblu

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    Re: Body Flex
    « Reply #5 on: October 12, 2012 - 06:43:04 PM »
    Quote from: XBRIT on October 12, 2012 - 05:51:35 PM
    Hi Guys,
    Factory construction no sub frame connectors and filler not lead.
    It looked to me as though moisture had got under the body filler and cracked the paint.

    Sub frame connectors are a good idea on these cars regardless of the engine.

    But my money is on the body filler. My '72, which basically has a stock 318/auto, has cracks and bubbles at the quarter seams. On my car it's 100% to blame on the crappy bondo job, as there's no way my 318 is causing any body flex.

    Lead is the proper way to fill that quarter seam if you want it to last.
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    Offline burdar

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    Re: Body Flex
    « Reply #6 on: October 12, 2012 - 06:53:46 PM »
    I've also seen a few people weld a metal strip in the seam.  There's nothing to crack then.
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    Offline 67vertman

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    Re: Body Flex
    « Reply #7 on: October 12, 2012 - 09:17:39 PM »
    I did all three to my car, torque boxes (front and back) frame connectors, and welded a metal strip on the roof to rear fender.  I am going to run a 500+hp, 535 ft lbs of torque 440 with a stick.

    We will see if they are a match to the all the twisting.

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    Ron - Born and raised in Southern California

    I got the 1970 Cuda, but still need the hot blonde to ride shotgun!

    First car -1969 Road Runner 383 4sp

    Current ride - 1970 Barracuda 440-6 4 sp Dana 60  (4:10)

    Offline HP2

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    Re: Body Flex
    « Reply #8 on: October 13, 2012 - 10:58:20 AM »
    These cars are 40 years old. They are built using spot welds. The panels move around just by driving, regardless of the power your engine makes. Think of it this way, a car built with spot welds is like all of your clothes being buttoned together.Sure they stay on, but they get gaps and flex that allow additional movement.

    Torque boxes and/or subframe conenctors are , IMO, mandatory on any build. At the very minimum, they stop creaks, groans, and rattles and improve panel alignment. In the best case, they prevent body damage and the need for repaints.

    If you want to see how much these bodies move, find the video on the XV Motorsports web site where they tested it. Without stiffening, these cars flex A LOT!
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    Offline larry4406

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    Re: Body Flex
    « Reply #9 on: October 13, 2012 - 07:55:56 PM »
    I am no expert., i think vinyl top cars got bondo equivalent at quarter to roof seam while hard top cars got lead.
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    Offline BIGSHCLUNK

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    Re: Body Flex
    « Reply #10 on: October 13, 2012 - 08:02:28 PM »
     :2cents:  I think these cars flex, motor combo nonwithstanding. Torque boxes help, but subframe connectors really step it up. All those old welds  :banghead: On a vert its worse. But I made my connectors out of $10 woth of steel. Dint cure the cracks I had... but they havent gotten bigger either. 
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    Offline 74BlueFish

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    Re: Body Flex
    « Reply #11 on: October 13, 2012 - 08:05:19 PM »
    My  vinyl  top had lead
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    Dan

    Offline rhamson

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    Re: Body Flex
    « Reply #12 on: October 15, 2012 - 11:30:08 AM »
    Quote from: XBRIT on October 12, 2012 - 04:23:58 PM
    It’s been a three year period after paint and my 72 E-Body has developed a crack in the paint at the body join roof to rear quarter panel.
    This was originally a 318ci vinyl top vehicle and the paint guy is questioning the motor I have now in the Challenger is too powerful allowing the body to flex and cracking the body joint in turn cracking the paint. It is running a 383ci 4 speed. He also said it could have been jacked up on that quarter twisting the body. I told him in 1970 they had a Hemi on the list of options, so my motor is not over stressing the body.
    Did they ever address this roof weld with different engine options?
    Cheers.
    Xbrit

     
    If you ever had the trim and inner panels off where the sail panel meets the quarterpanel inside you would see that the only thing holding that area rigid is a quick weld drop that allows everything to flex and move till you get to the seam on the outside. I am going to weld this area solid and re-enforce it with a peice underneath it so this doesn't happen again. I have had two Challengers with both having the same problem. I think the unibody flex is what makes this happen. Both of mine were filled with body filler but both had prior bodywork when I got them. If you look closely to the outside edge where the quarterpanel meets the roof going up you will see a crack forming on the right. The panel doesn't have a chance of not showing a crack going up the seam.

    As to whether the horsepower options changed the body flex I don't think that makes any difference. The first '72 Challenger had a 440 Magnum with an automatic swap from a 340 automatic and the crack was there and the second one I now have had a 340 automatic in it with the same tell tale cracks. It is a design flaw in my reckoning. Maybe it won't help with your body man if he did a restoration conscious paint and body job on your car.
    « Last Edit: October 16, 2012 - 09:43:18 AM by rhamson »
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    Offline johns cuda shop

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    Re: Body Flex
    « Reply #13 on: November 01, 2012 - 04:57:45 PM »
    Quote from: burdar on October 12, 2012 - 06:53:46 PM
    I've also seen a few people weld a metal strip in the seam.  There's nothing to crack then.
    I agee, this is a good method but you need to media blast the weld clean so the primer and bondo doesnt lift. If it a black car I would refrain from mig welding on the upper outer sheetmetal because it will show thru on a sunny day, this is because the mig weld is a harder weld than the sheetmetal itself and expands different in the sun. Just food for thought
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    71 Cuda Gen III Aluminum 426 Hemi T56 6 speed 4.10 8.75 Modified & Lowered RMS coilover suspension Wilwood discs

    Offline rhamson

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    Re: Body Flex
    « Reply #14 on: November 02, 2012 - 09:43:57 AM »
    Quote from: johns cuda shop on November 01, 2012 - 04:57:45 PM
    I agee, this is a good method but you need to media blast the weld clean so the primer and bondo doesnt lift. If it a black car I would refrain from mig welding on the upper outer sheetmetal because it will show thru on a sunny day, this is because the mig weld is a harder weld than the sheetmetal itself and expands different in the sun. Just food for thought
    I agree also as I have seen the effects of this seam coming through on a hot sunny day on a dark colored car. I am going to lead this seam in once I weld the joint inside the window area. I have seen this done with black cars so I know it works.
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