81 frame cracked

big2bird

Charter Member, Founder Bird-Run, Cruise-In Bird-R
Joined
Mar 5, 2008
Messages
5,719
Location
Anaheim, Ca.
So, I am doing some PM work on the 81 today, and I find this on the pass side. Extends down and to the spring pocket. $50. at my favorite welder, and it's all good. Now, the question. How common is this? I am sure it was not there before the last Bird Run, but it could have been there as a stress crack for awhile.
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To much HP and you are twisting the frame,i suggest you tune the motor down some.

:lol::lol:
 
I had a small crack on the bottom of the frame in that area.
 
Apparantly it's common as hell in the later cars. My '65 had a '74 frame that was cracked all over in the front. Thats why I'm changing it right now. Found a real nice '65 frame
 
I'm helping a buddy with a 63 and was amazed at how much better the welds on his frame are than on ANY C3 frame I've seen. He has actual welds, not porous blobs of metal.
 
1) So is there any gussets I can add to prevent this?:crap:

2)I never had any cracks till I added the spreader bar. :blush:Coincidence?
 
Suspend driving priviledges. :waxer:

Instruct to stay away from curbs, potholes and shoulder drops. Drivers side ok.



Not worth the hassle with the body on, just keep regular inspections.
 
1) So is there any gussets I can add to prevent this?:crap:

2)I never had any cracks till I added the spreader bar. :blush:Coincidence?

i would think you could take some 3/16 or 1/4 plate and weld it to the outside of the frame as a strengthener and stiffener. You should have asked your welder guy.
 
1) So is there any gussets I can add to prevent this?:crap:

2)I never had any cracks till I added the spreader bar. :blush:Coincidence?

i would think you could take some 3/16 or 1/4 plate and weld it to the outside of the frame as a strengthener and stiffener. You should have asked your welder guy.

I may have to do that. I can't help but conclude that the spreader bar , after boxing the front end, has increased the stress to another place. Installation of a spreader bar may entail other married upgrades to insure reduction of failure.
 
[. I can't help but conclude that the spreader bar , after boxing the front end, has increased the stress to another place. Installation of a spreader bar may entail other married upgrades to insure reduction of failure.

I took mine off a long time ago. You could really see how flexible the frame was adjusting it. I could significantly change the camber with the bar.
 
I took mine off a long time ago. You could really see how flexible the frame was adjusting it. I could significantly change the camber with the bar.

Wouldn't that say that the spreader bar is doing its job tho? Isn't it supposed to ridgid everything up and prevent 'variable camber'?
 
Jeff, how did you adjust the spreader bar? Did you tighten it down a few turns after it was snug? with the fine thread and the high mounting position it doesn't take a lot of force to bend the frame and cause excessive stress. I set them by setting the suspension and tightening it until you see the numbers change on the alignment bench, if they change just a hair I tighten it down. It doesn't need a ton of preload, snugged up is just fine. It's going nowhere after that.

I can't think of a gusset you could easily place there to help that area, only viable thing to do was to roll/bend a piece of angle iron to closely fit the contour of the spring pocket and weld that on. That should help. Also do check the inside of the spring pocket to see if the crack is visible there too.

That crack you have originates in the spring pocket, did they weld it there too? The metal is really thin and the stamped pieces have very sharp and sometimes rough/serrated edges, very easy for a crack to form.
 
Jeff, how did you adjust the spreader bar? Did you tighten it down a few turns after it was snug? with the fine thread and the high mounting position it doesn't take a lot of force to bend the frame and cause excessive stress. I set them by setting the suspension and tightening it until you see the numbers change on the alignment bench, if they change just a hair I tighten it down. It doesn't need a ton of preload, snugged up is just fine. It's going nowhere after that. I turned it out by hand, then locked it down. I didn't use a wrench at all.

I can't think of a gusset you could easily place there to help that area, only viable thing to do was to roll/bend a piece of angle iron to closely fit the contour of the spring pocket and weld that on. That should help. Also do check the inside of the spring pocket to see if the crack is visible there too.

That crack you have originates in the spring pocket, did they weld it there too? The metal is really thin and the stamped pieces have very sharp and sometimes rough/serrated edges, very easy for a crack to form.
We welded it up to the edge of the pocket. I did not pull the spring out. It's a 450lb spring BTW.
 
it interfered with the mechanical fan. I had an extender on the fan clutch. It wobbled and sent a blade right through the radiator.

Ain't that nice... I love that sound. I did that once on a street rod. Mounted my flex fan real close to the rad. Lived out in the country at the time. Got out on the hiway, Flex fan flexed right into the rad. ZINGG..... Turned around and went home again.:banghead:
 
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