Tunnel crack - fixable?

[Razorrock157]

1961 bug. Pulled rear seat and found a crack in the tunnel. Any suggestions on fixing it properly? Welding for sure but how to make it structurally sound.

[esde]

weld the crack, grind flat, and then bridge the crack with a larger piece of steel and weld that. You'll have to trim the bridge so it doesn't get too close to the vin number, and take photos of before and after so nobody questions the authenticity of the vin number
I'd probably use some 1/8" for the bridge piece, and have it go about an inch past the crack where possible
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modok wrote:
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[finster]

why would it crack there? is there likely to be damage elsewhere?
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[MikeGyverOG]

That seems like an odd place for a crack without substantial damage somewhere else.

[SLO-N-LO-69]

I can honestly say I've never seen a crack there ever. Rust yes but never a crack. I would make darn sure there isn't something else bent or damaged before wasting my time fixing it only to find it was crooked to start. That must have been a hell of a wack to crack there.

Unless this is some family heirloom or special vin I would probably just get a new chassis and start fresh.

[Razorrock157]

Thank you for the info. The car was hit square on the rear bumper. The bracket is bent an inch or so. The apron and rear fender had minor damage. I figure the accident jolted the chassis hard enough to crack the tunnel. Weird spot. The doors have normal operation and gaps.
I have the original matching numbers 36hp motor with it. Shame to scrap it.

[KTPhil]

Something else caused this damage.
The force path for a rear ender to that part of the chassis would be:
- bumper... body... body mount... chassis. But the body mount bolts would shear before this crack could form, and the whole rear body structure would be crushed
- engine...tranny...frame horns... chassis. But the engine would be utterly smashed by then.
This was dropped or otherwise impacted independent of a fender bender. I would go over the chassis and all its welds very carefully to look for the rest of the damage before dong anything else, preferably body-off.

[my59]

Was this car parachuted out of a plane? Holy Moly!
The triangle shape with the missing shard on top, this thing took a real smack.
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[Loren]

It almost looks like some one used a plasma cutter on it. Can you feel or see any slag on the back side of the crack? Likely a long shot, but worth a look.

[EVfun]

What I would do...

1. Grab a fairly power magnet and hold it about 1/8 inch above the surface and pass it all around the crack and whole general area. I'm looking for other steel. I would concerned if I found a number of steel balls or steel filings on the magnet as that indicates previous repairs in the area.

2. I would clean that area up really good. I would light it up well and take a bunch of pictures. Now I'm documenting the "as discovered" state. If you you got any metal bits above photograph them too. If you need to look back while doing repairs it is nice to have documented the starting position. Not really that practical 30 years ago -- but I embrace this tech now!

3. Anything you can do to see inside the tunnel for damage and signs of previous repair. If you find it then you should try to figure out how to photograph it too.

4. Any underlying problems found should be fixed. If it is just body rust leaning on the frame too much that can wait, but a message has been sent.

5. Clean up the area around the crack to shiny steel. Drill the ends of the crack(s) with a 1/8 inch drill to "drill stop" them. Then weld that shit back together. Do it well and don't hide it, it will always be obvious from the reverse side because if all went well you will have through weld penetration.

6. Marvel at how tough these little old cars really are! You might mix this step in with all the steps above. WOW, I've never seen that crack.
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[Busstom]

Just a couple of things to note which I don't think have been mentioned yet....
That crack looks ancient, it's had plenty of time and movement to cause it to open up significantly; it's been there long enough to rust to the point where the fracture lines are no longer jagged, but sort of smoothed over; it's also old enough that it has accumulated quite a bit of dirt and debris. In the upper-left quadrant of the photo, where the crack transitions up from the vertical wall to the horizontal top surface of the tunnel, there almost appears to be a hole, as if someone tried to drill a hole to stop the progression of the crack long ago. And finally, the area at the lower-most part of the crack, down on the sidewall of the tunnel, has had time to bulge outward toward the battery area, which, along with the wide-open nature of the gap, suggests to me that the right frame horn and torsion tube have been flexing quite a bit and torquing on this area for a long time.

Those are just my observations. They don't change anything already suggested about repair options, but at at a minimum, if you plan to weld the crack, you really want to clear as much rust as possible from the cross sections of the metal (the actual fracture surfaces), the last thing you want is for the weld to be contaminated with iron oxide. And before that, some serious measurements of the frame horns, torsion tube, and general chassis/spring plate alignment verification.
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My name's Steve and it's pronounced "Bust 'em" (cuz people think I'm Tom) 😏

[Dusty1]

[splitjunkie]

[Pruneman99]

It looks like a plasma cut to me as well. I think I'm seeing slag balls spread around the cut. Next to the triangle piece, it looks like it's welded back together in a spot. All the way to the right side of the cut, it looks like melted metal that wasn't blown all the way out by the torch.

Or I could just be seeing what I THINK I see.

Either way, that's a very strange place to see a crack, or a cut.

[Dusty1]

[Busstom]

As everybody seems to agree, an impact great enough to initiate such damage would've left other signs of damage. So in my opinion, I believe the most plausible explanation is just a defect in the manufacture of the raw material, totally undetectable when new. Then the passage of time and stresses just caused the defect to propagate to what it is now, and it just went unnoticed and/or disregarded for decades since the only time the average person lifts the back seat is to service the battery or shift coupling, for the most part. Out of sight, out of mind. Even if it was noticed, and depending on by who, they probably didn't worry enough to take action or consider it necessary to remedy. After all, it's still holding up, let the next guy (Razorrock) worry about it
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My name's Steve and it's pronounced "Bust 'em" (cuz people think I'm Tom) 😏

[Dusty1]

Link

[splitjunkie]

[Dusty1]

[Busstom]

Why would somebody even take a plasma cutter (that is, if they were even commonplace back in the day when this crack occurred on this vehicle) and just decide to say "Hey, I'm gonna go to the back of this pan tunnel, fire off my plasma torch and make a jagged, squiggly zig-zagged cutline, have a good laugh out of it, and then drop the seat back down and pat myself on the back, cuz I know how to use a plasma cutter"? Who would do that? Probably nobody.

That just makes absolutely ZERO sense at all. Yes, people have done stranger and stupider things, but I just can't believe that this is one of them. It has zero plausibility.
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My name's Steve and it's pronounced "Bust 'em" (cuz people think I'm Tom) 😏