cracks in frame rails

[dutch]

hi there,

last weekend I put my 1970 cuda in the rotisserie and when I turned it over I found cracks in the front frame rails. The cracks are located where the rear bolts of the k-member are. As far as I can see everything is still in place and the body hasn`t bent. The doors and fenders are still on the car.I cannot find any traces of accidents but the k-member has some dents and scratches. Maybe someone seriously miscalculated a hole in the road?... Have any of you seen this before? Is this probably due to abuse, or is it metalfatique?

[Chryco Psycho]

it could be rust inside the rails weakening  the frame to the point where the frame has split relatively easily , you may have to cap or replace the rails , check it carefully for thickness & rust

[dutch]

...no rust in and out...not even a tiny spot...
the k-member bolt were pretty loose though, and on the surface where the member touches the rails the metal is polished...
maybe this could be the reason for cracking? I can weld the cracks well, esp. now the car is op side down, but I wanted to check if this is a common problem on these cars before doing so...

[moparclown]

I have seen this a couple of times now,Kinda spider web cracks?Just a pointer,before you weld those cracks up.At the end of each crack,drill a small hole and then weld them up.

[dutch]

jeb...spiderweb...

I will spray with contrast fluid first, so I can see where the cracks really stop, then drill holes and weld.
@ moparclown;  since you have seen more cars with this problem, have you also had a chance to what happened after welding over a longer period of time?
thanks for your reply

[fishn4cuda]

hi there,

last weekend I put my 1970 cuda in the rotisserie and when I turned it over I found cracks in the front frame rails. The cracks are located where the rear bolts of the k-member are. As far as I can see everything is still in place and the body hasn`t bent. The doors and fenders are still on the car.I cannot find any traces of accidents but the k-member has some dents and scratches. Maybe someone seriously miscalculated a hole in the road?... Have any of you seen this before? Is this probably due to abuse, or is it metalfatique?

I see them all the time. Definately stress cracks. Not sure what causes them, but I just weld and blend the area off. Very common.

[ragtopdodge]

Pics?

[dutch]

http://i246.photobucket.com/albums/gg101/smidje71/DSC00679-1.jpg
http://i246.photobucket.com/albums/gg101/smidje71/DSC00680.jpg
http://i246.photobucket.com/albums/gg101/smidje71/DSC00681.jpg
http://i246.photobucket.com/albums/gg101/smidje71/DSC00684.jpg

[farmboy70]

As said before drill a small hole at the end of the crack and weld them up. Should end any more problems. If the K frame was a little loose it probably caused the cracks.
Dave

[71bigblock]

Ok I'll bite.  Why drill the hole?   

To assure it wont come back I assume.   

[bb71challenger]

Ok I'll bite.  Why drill the hole?   

To assure it wont come back I assume.   

Exactly, the hole stops the crack from spreading any further.

[moparclown]

Most of my crack background :crazy:came when I worked on snow grooming machines(snow cats)and when you welded it up without drilling that relief hole,it would come right back.As far as for any time check on frame rails,I never doubted my fix and haven't had any comebacks :cooldancing:I hope this helps
                                                                       The Clown

[dutch]

thank you all, I`ll start working on it this weekend.

[miketyler]

stop drilling cracks is common sheet metal practice in aviation. Stop drilling at the both ends releives stresses local that would allow the crack to continue. However, I have seen cracks continue past stop drills. 

[hemiken]

Hi Dutch,
Can you download a picture of the area that is cracked please.