Body Stress Cracks - Team Camaro Tech
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post #1 of 19 (permalink) Old Mar 13th, 00, 11:51 AM Thread Starter
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Since I asked this question before I've been looking more closely at 1st and 2nd gen Camaros. Pretty consistently I've noticed hairline cracks coming from the 2 upper windshield corners and the rear window/drip rail point (at least the left side). I also have seen cracks running through the leaded quarter panel/roof joint!

First question is - can some of you check your cars and tell me if you have the same kinds of cracks?

Next - what happens over the years - do they get worse - or stay the same after the initial stress relief?

Finally - anybody come up with a way to prevent or minimize this problem? I have subframe connectors bolted in - does welding them help?

------------------
Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
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post #2 of 19 (permalink) Old Mar 13th, 00, 01:25 PM
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I have hairline cracks on my 68 in that seam where the rear quarters meet the panel directly behind the rear window. I noticed this after I put the 468 in, I don't know for sure if the extra torqe did this or just normal wear. I did'nt think there would be a problem since I just run radials, but I have put bolt in subframe connectors and I will be welding them very soon. I don't think they do to much good if you just bolt them between the body bushing, adding the extra bolts through the front subframe should help but I would rather just weld them in.

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post #3 of 19 (permalink) Old Mar 13th, 00, 02:49 PM
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This definitely is a motor torque issue. You should put sub-frame connectors on anything that has more than say 350 ft.lbs. of torque. The engine torque TWISTS the body in the areas that you mention because as you know the camaros do not have a full frame underneath them but depend entirely on the body structure to tie the front sub-frame to the rear suspension. You should also weld the sub-frame connectors on to completely eliminate this problem. You can LEAD the cracks in after the sub-frame connectors are in place and welded and this should not occurr again.

Secondly,

Chevy had a torque limiter cable that they installed primarily on their big block Camaros by the passenger side motor mount that "limited" the amount that the motor could rock over to driver's side. You will see these from time to time on EBAY. They DO HELP.

You see this body cracking alot on cars that originally had small blocks but now have stroker motors or big blocks. Convertibles had a reinforcement piece that fit underneath the body area of the car that gave it some needed additional structure BUT it is still not enough for a torquey motor.


[This message has been edited by sr71bb (edited 03-13-2000).]
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post #4 of 19 (permalink) Old Mar 13th, 00, 04:55 PM Thread Starter
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Thanks for the responses! All the cars I've seen the cracks on are running >400 hp. I will have my subframe conectors welded in but I also wonder if the connection to the rear frame (bolts thru the front spring bracket) is enough? I don't want to get carried away but I can't get excited about my car getting laced with cracks either.

------------------
Scott
'69 400SB, Richmond 5-speed; '99 HD Road King Classic
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post #5 of 19 (permalink) Old Mar 13th, 00, 05:04 PM
 
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Those cracks do look quite unsightly on my black paint, don't they??

With respect to sr71bb's comment about the torque limiter cable- I'm not sure I understand how this device would lessen the amount of torsion between the front and rear of the car. Since the cable provides a fixed link between the engine and the subframe under torque, I would think this would actually contribute to the torsion, while the engine mounts act more like springs, which would absorb some of the energy...?

If this were true, I would think welded subframe connectors would be the optimal solution.

-Dave
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post #6 of 19 (permalink) Old Mar 14th, 00, 02:00 AM
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i have the same problem with the top of my windshield. i fixed mine, have a welded subframe and they still came back. mine are partially hidden by my vinyl top, but i know there still there and don't know how to fix them, except to welded a larger piece over top of them and drill small holes at each end of the crack to act as a stop. other then that, i guess i'll have to deal with it.
later,
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post #7 of 19 (permalink) Old Mar 14th, 00, 02:29 AM
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Another consideration is what type of body bushings you have. Art Rasmussen, Global West, etc. state that solid bushings are mandatory with welded connectors. They state that otherwise floor cracks will develop. I would assume this could pop up elsewhere. con
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post #8 of 19 (permalink) Old Mar 14th, 00, 06:22 AM
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Is this true? Global West and Art Rasmussen state that solid body bushings are mandatory? I'm about to install the weld-in type connectors that Art has dicussed in this forum that weld to the back of the subframe, go through the floorboard, and weld into the leaf spring torque box. I have polyurethane body bushings but now I am concerned about metal fatigue cracking at the torque box. Any thoughts?????

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post #9 of 19 (permalink) Old Mar 14th, 00, 09:19 AM
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i have ssm weld in connectors on my 67 with urethane body mounts, i still have the hairline cracks in the windshield pillar on both sides, they never seem to get worse, i just live with it.

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post #10 of 19 (permalink) Old Mar 14th, 00, 02:02 PM
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I would suggest calling Art Rasmussen. Don't have his # handy. Global West did not state consequences, Art did and was specific in recommending solid bushings.
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post #11 of 19 (permalink) Old Mar 14th, 00, 04:52 PM
 
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Did Art recommend what material to use for the solid bushings? I have seem aluminum bushings but I think bronze would be better because it self lubricates. Does anyone know a company making bronze bushings?

Joseph
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post #12 of 19 (permalink) Old Mar 14th, 00, 06:17 PM
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Joseph, I'd go with solid full height aluminum bushings.
My 67 had a lot of cracking just below the rear window, and where the rear quarter panel attaches just outboard of the taillights. But I did a lot of autocrossing with 10" slicks all around. and about 425 hp.
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post #13 of 19 (permalink) Old Mar 15th, 00, 02:20 AM
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The Global West ( which I bought ) and Art's are aluminum. Global makes stock height ( which I got ) and 1/2 " lower which they did not recommend for me. I'm not sure what the height is on Art's.
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post #14 of 19 (permalink) Old Mar 15th, 00, 04:34 PM
 
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David,
Why do you recommend the stock height bushings? Is it because the front sheet metal will not line up properly with the lower/shorter bushings? I read in the Guldstrand catalog that the shorter bushings increase the rate of the front end. I am assuming that this is benificial to handling but unsure as to the consequences for every day street driving.

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post #15 of 19 (permalink) Old Mar 15th, 00, 05:09 PM
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Well, the conversation got a little off track from the original question, but I wanted to add that my car has developed cracks on both A-pillars at the roof line, cracks at the seams between the rear quarters and piece that goes between the rear window and trunklid on both sides, and is starting to form cracks from the corner of the quarter windows where they meet the quarters. They really make me angry since they show up as black on my white car (they attract dirt that is impossible to remove). I guess this is a torque issue in my car, as i have broken 2 drivers side motor mounts in the past 6 months??? I also would like to add that i don't understand how a torque limiting cable would work on the PASSENGER side of the car. My engine rocks TO the passenger side of the car under torque, hence the reason I broke 2 motor mounts in half. Just my thoughts.

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