JB Weld – Strong Enough To Repair a Connecting Rod?

JB Weld is a particularly popular brand of epoxy, and features in many legends. “My cousin’s neighbour’s dog trainer’s grandpa once repaired a Sherman tank barrel in France with that stuff!” they’ll say. Thankfully, with the advent of new media, there’s a wealth of content out there of people putting these wild and interesting claims to the test. As the venerable Grace Hopper once said, “One accurate measurement is worth a thousand expert opinions“, so it’s great to see these experiments happening.

[Project Farm] is one of them, this time attempting to repair a connecting rod in a small engine with the sticky stuff. The connecting rod under test is from a typical Briggs and Stratton engine, and is very much the worse for wear, having broken into approximately 5 pieces. First, the pieces are cleaned with a solvent and allowed to properly dry, before they’re reassembled piece by piece with lashings of two-part epoxy. Proper technique is used, with the epoxy being given plenty of time to cure.

The result? Sadly, poor — the rod disintegrates in mere seconds, completely unable to hold together despite the JB Weld’s best efforts. It’s a fantastic material, yes – but it can’t do everything. Perhaps it could be used to cast a cylinder head instead?

24 thoughts on “JB Weld – Strong Enough To Repair a Connecting Rod?

    1. I could see a microphone on his person, most likely, he was relying on a camera’s built in microphone Not like this was recorded on sound stage Perhaps there is software that can be used after recording to clean up the audio, but why expect the effort on free content?

  1. I didn’t watch the video because apparently the guy is shouting and it didn’t work, but what did work was plugging an impact hole in a unimog fuel tank, and rather surprisingly having removed the auto advance device from the side of a DPA pump I filled the remaining hole with jb weld which helt the cam ring in place and didn’t leak diesel everywhere.

  2. Is anybody surprised that i did not work? I certainly am not. I do wonder if casting an entire new rod out of jb weld would do better. I think it would, but it would still fail when it got hot or id it had to produce any torque.

    1. Forged metal tends to work. Even actual welding of the non-JB variety isn’t likely to work well in this case, goops and putties are a funny diversion but there’s just no chance.

    2. No epoxy does well in a hot hydrocarbon bath with lots of expansion and contraction going on, plus they need some “thickness” to provide a good bond — and moreso if they are “filled” as JBWeld is. Something like a con rod needs a “zero thickness” repair.
      A cyanoacrylate adhesive (Super Glue) could get close to that zero thickness thing, but it’s very brittle; I suspect it would last for about two revolutions.

      1. It’s not the hydrocarbon bath or the heat, I’ve plugged transmission cases and oil pans with it. Probably the tensile hammering a con rod gets.

        There are ways to use JB Weld and this wasn’t what I’d have done there if I had to, an emergency repair, I’d have been bonding straps and patches of metal over it with it.

  3. I’d be much more interested in a connecting rod cast from JBW with a proper bearing. Even if that ‘weld’ had held, the bearing was toast and would’ve frozen and cracked off some other piece.

    1. That logic reminds me when my astrologer said capricorns were going to have a lucky day; and since I’m capricorn I went to work with a smile on my face, thinking something awesome could happen. When I was on my way, my car broke, “how can this be?!”, I said, and then I called my astrologer asking him how is possible my car broke on my lucky day. His answer: “Your car is not Capricorn”

  4. Pretty obvious this would not work, I did however patch a hole in my buddies oil sump with a cut up beer can, a rock off the road to rough the area, vodka to clean the hole, and some JB weld. It never actually failed, the surprising thing was his farmer father did not approve even though it got him 200 some miles down the road. “That’s not how you fix things,” well it is when its all you have and you need to be at work the next morning.

    1. Field repairs. Decades ago I was with a friend in his car out in the middle of nowhere in Kaycee Wyoming when he went over a big bump and broke the connection to his muffler. For some reason he was pissed at me. He was non mechanical so I let hm stew in it for a bit and try the first fix. After about 2 hours he was ready. I asked him how he fixed it. It was easy, there is a big pipe that goes right over the exhaust pipe and I lashed it onto that. Um, you do realize that that pipe, um spins when the car moves… He now was *really* unhappy with me. So I took a stab at it. There was an old rusted out fence so we had lots of fence wire. We had lots of aluminum soda cans. We had lots of mud, we had some metal skewers and roll of aluminum foil for cooking.. His moronic fix was actually helpful as it kept the parts aligned, even thought I had to tear it out before we actually took off. He lucked out in that the crack was on a long piece of pipe going from the engine to the muffler so there was a lot of area on both sides to wrap stuff around. Soda cans with mud and the skewers to keep things aligned, lots of fence wire, aluminum foil over that, more fence wire, and another go round of cans. The repair was thick but the car purred and we made it another thousand miles until he decided he needed to get it “fixed”. That took a few stops to find someone who was both inexpensive and willing to weld near the gas tank that one guy said was weeping a bit. He got it fixed. Everybody got a good laugh out of my fix. 300 miles down the road the welding job failed going over a bump. My fix may have been ugly, but it was flexible.. I wound up taking greyhound back home. Depending on where you are you fix things as best as you can.

  5. I’m sure JBW’s business plan is to hype up the product, and because it’s so cheap people go; its worth a shot if it works it works, if it doesn’t work not out of much There is going to be enough hits to validate the hype. The sort of surface cleaner that give adhesives the best chance of working are too expensive for use on stuff like this

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