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Post by Hs1973 on Wed Jul 18, 2018 9:37 am

Hi guys. i have a warning i feel i need to post up here, im sure some of you Might say its a no brainer. And maybe it is, but i made the mistake anyway so im posting it here just in case so you all can awoid doing the same.

5 years ago i totally restored my 75 chevelle, frame off from the Ground up. I took a close look at the frame and Found no rust or other damage, however i did notice that the factory welds where a little so and so, Lots of Big bird droppings and overall not pretty. So i Ground off the worst and decided against rewelding it since it looked fine after 40 years of service. That was a BIG mistake. Next thing was the bars that reinforce the frame from behind the lower front control arms forward under the engine. They where bend and rusty so i used some stainless tube i had laying around, that was mistake number 2. It turns out the bars i made had a flaw, 1 i made the mounting holes to Big and 2 they are to weak. So no i have a Big crack in the frame on the underside next to the rear mounting point for the lower control arm.

I have been chasing a clunk sound present when i would back out of my driveway, i have ben fokused on the suspension, and Found some issues with my upper control arm bushings. I fixed it but the clunk did not go away, today i was under the car to retighten some bolts in the suspension and noticed a dime sized hole and a crack the seams to get worse. After putting the old reinforcements back on the frame, the clunk is gone. And i need to repair the frame.

So beware that even a sound looking frame can break, if you are not careful what you do.

Crying or Very sad
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Post by Joe73 on Wed Jul 18, 2018 9:45 am

Bad factory welds are a problem that I have not run into on any of the the frames I've dealt with. But your issue up front with the lower support bars puzzles me. I've removed those bars when I got my car in 1982 to install long tube headers. My monte did not have them either. I've never had an issue with frame cracking, twisting or otherwise up there. I did have issues with the front mount of the REAR lower control arms. I've ripped that off the frame a couple times but that was from years of dumping the clutch.
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Post by thatfnthing on Wed Jul 18, 2018 10:07 am

I've always been of the mindset that the factory didn't give you anything you didn't absolutely need.

Especially given the bare-minimum testing they used to do back then, if they decided to add those lower support bars, then it needed them.
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Post by Joe73 on Wed Jul 18, 2018 10:34 am

thatfnthing wrote:I've always been of the mindset that the factory didn't give you anything you didn't absolutely need.

Especially given the bare-minimum testing they used to do back then, if they decided to add those lower support bars, then it needed them.

I agree !!! I would like to install them but if I remember correctly one side wont fit with the long tube headers. Shorty or mid length are not an option with Z-bar linkage. I'll take a better look when the engine goes back in.
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Post by Hs1973 on Wed Jul 18, 2018 12:40 pm

I caught it before it Got worse and is still a fairly easy fix. And i wish i could show you a picture, but im not cleaver enough to post pictures. but i can see how the weld is almost not present at the spot where it startet braking. The clunk sound was from the mounting point in the bar moving under load because the bolt was not tight enough. The bar eventually startet to bend under the load wich eventually made the frame crack. So if i had the original bars in place and a sound weld plus made sure my whoa nelly was tight from the start, i would not have a crack in my frame now.

So now im going to fix the crack and reweld the frame at the mounting points. And make sure everything is tight so i can be sure to awoid cracks in the future.

Im pretty sure everything would have been fine if the weld had been better from the beginning. Could the fact that i had it lowered and alot stiffer front springs in it last year have contributed to the failure???? Since Joe can run his without the bars alltogether???? Or could there be something Else i have missed.
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Post by Hs1973 on Wed Jul 18, 2018 12:43 pm

Also i have heard of frames brake in the back, or ripping rear mount ears off. But this surpriced me alot bit im glad i Found the problem at least. Im also getting new bars made that are stronger than originals both front but also for the rear of the frame at the weak mounting ears. And i agree the factory did not provide things unless its a necessery,and i did get it almost right. I put the bars back in but just dident do it right.
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Post by thatfnthing on Wed Jul 18, 2018 1:58 pm

Hs1973 wrote:Could the fact that i had it lowered and alot stiffer front springs in it last year have contributed to the failure???? Since Joe can run his without the bars alltogether???? Or could there be something Else i have missed.

My guess is the lower support bars were primarily to combat cornering forces.  With those skinny tires up front, I think Joe only goes in a straight line. Very Happy
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Post by Hs1973 on Thu Jul 19, 2018 3:10 pm

Yeah you are problely right. I can only guess as to why it cracked. Im going to fix it and strengthen it so it does not happen again. I have had at least 35-40 different USA cars over the years, a dozen mopars, at least 10 different chevys and plus the mustangs, cougars, trucks and this is the first time i have had a frame crack on me. But im guessing it had a week spot there that just gave up.

I Googled it and it seems it is more normal for a frame to crack or break than i initially thought. But i have just learned something new, and i discovered where the clunk Came from at last.

Besides the bars is there a another Way to beef up the area that anyone knows about? Any info is welcome.
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