Everyone jokes about JB, but
 

It seems to work OK.

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We were discussing this today at work. One of our power plants buys Flex Seal in large quantities and successfully uses it all over the plant. The stuff ain't cheap either.

Well...JB has been known to axe fer it....I believe it wuz his earz .... but I dunno?

He's OK now though.....I hope ;)

Same guy cut a slot in a lawn mower head and then filled it with JB Weld and ran it for 20 minutes.

So, this thread is not everyone Joking about Joe Bob???????

Many years ago I was building a no expense spared engine for my RX7.

My goal was 500 to the wheels in a 2600 lbs car.

We knew we were going to have to do a very aggressive porting job on the engine, we debated templates and chose what was called an aggressive street port. It was the limit you could push on a street driven car.

I owned another RX7 that had 500RWHP and the port job on that was so over the top it had no power down low you have to rev the piss out of it (over 5K RPM) to make it move but man, it moved!!

My goal was to make a more street friendly version of that car. I spend years researching turbo's stand alones, injectors fuel delivery etc..

So I told you all that to tell you this.

When it came time to port the engine, we knew we were going to cut into the water jackets near the intake ports. The solution online was JB weld.

We refused to accept that, JB weld is duct tape in a tube.

I purchased some very expensive epoxy to try, I think I spent over $150 for a small can of it. We tested it alongside some other brands we purchased along with some good old JB Weld.

We put them all on a piece of metal similar to my engine internals then put them in boiling water with gas and oil in it to re-create the environment the epoxy would be forced to live in.

Everything failed except the JB. Still unconvinced even though I just saw with my own eyes the result I tracked down two of the best Rotary engine builders in the business. Both use JB Weld.

So we used it. 14 years later and about 30K miles later many track days Autocrosses and wild mountain runs with some Pelicans in their 911's, it is still holding up.

I am sad to report I did not achieve my 500RWHP goal the best we could get was 490. If any of you are familiar with rotary engine tuning, you hit a point where you say, "OK That's good I am not interested in pushing further"

JB Weld is amazing.

maybe they boiled him down into glue

So...

Cement is a powder that when mixed with water forms a supersaturated solution that turns into limestone crystals. Limestone is not super strong. Concrete is cement mixed with small rocks known as aggregate. The cement forms limestone crystals around the hard stone aggregate. concrete is very strong, for a variety of reasons, mostly having to do with the aggregate.

Epoxy is a catalyzed plastic. JB Weld is epoxy with steel filings as aggregate. Fiberglass is epoxy with glass fibers. Epoxy isn't inherently strong, but it is a good binder. Carbon fiber, glass fiber, and steel filings are all inherently strong. Epoxy binds them, and gives them form. JB Weld isn't epoxy. It is steel, with epoxy as a binding agent.

I wish I'd known that 15 years ago when we did a peripheral port on a 3 rotor 20b engine. We used fancy Devcon titanium epoxy which actually held up fine.

The guy that did my heads uses JB for his port tuning. He uses it to shape it how he likes for proper flow. He must know what he is doing, he has built some engines that have set speed records.

JB doesn't hold very long to aluminum or glass tho'....anything with a beer in it ;).

Wankers .

I'd like to see the ratio of ingredients by volume for the resins, steel particles and other fillers. I think you are correct about the binding aspect but I'd fall short of calling JB "steel."

This may be of interest as no "steel" or even AL particles are mentioned:

What is in JB Weld?
Bisphenol-A-(epichlorohydrin)
The resin in J-B Weld epoxy is bisphenol-A (yep, that BPA) combined with garlicky-smelling epichlorohydrin. Chemically, the molecule is a chain with little carbon-and-oxygen triangles, called epoxide rings, on the ends. That’s where the sticky action happens.

Crystalline Silica
Basically quartz. It’s added to the resin for body and viscosity, without which the goop would be too fluid to adhere and set properly—more like J-B Melt.

Carbon Black
The name says it all. Made up of sooty bits often produced by burning hydrocarbons, it gives the resin its inky color.

Calcium CarbonateA cheap filler, found in both the resin and the hardener. Like the silica, it gives the product more volume while decreasing the cost per ounce.

Tetraethylene*pentamine
This is the curing agent. It contains amine groups that break open the epoxide rings so their carbons can hook up with the amine’s nitrogen. One TEPA molecule can lock onto four epoxy resin chains, and the other ends of those chains can bond to other TEPA molecules. All that cross-linking forms a super-strong network structure—a thermoset polymer. When it hardens, J-B Weld can withstand forces of nearly 2 tons per square inch and temperatures up to 550 degrees Fahrenheit.

DMP-30
The curing agent on its own is kind of lackadaisical at opening the rings, so epoxies often use accelerators like this one. DMP-30 is short for 2,4,6-tris(dimethylaminomethyl)phenol. It has a reactive hydroxyl group (–OH) hanging off the side that helps rip those epoxide rings open like Christmas presents.

Benzyl Alcohol
This colorless liquid modifies viscosity and acts as a solvent to help the curing agent disperse during mixing. Like DMP-30, benzyl alcohol also has a hydroxyl group that can trigger curing, so it’s put in the hardener tube.

Titanium Dioxide
This stuff adds more body to the mix, and it turns the curing agent a color-coded white. Mix with the black resin and you get that famous gray.

Barium Sulfate
More filler. BaSO4 is radiopaque, which is why they make you swallow it to x-ray your innards. Pro tip: Do not attempt this with J-B Weld.

Source: https://www.wired.com/2016/08/whats-inside-industrial-epoxy-bpa-somethin-garlicky/

^ Great info. That video is very impressive too. Suspect that the Gorilla Glue on wood would have worked better if they wet the wood with water before gluing (per the instructions), but clearly JB reigns supreme for most uses.

I always wondered if this would hold up in air cooled heads that typically run much hotter than water cooled heads.

I used it to make a modification inside a gun :eek: and it's held up well. Imagine the heat and recoil.

Oh yeah! Is JB still making graphics? I need some stickers for a bike. If he's not serving time in some Mexican carcel, or dealing in some Mehican cartel, I need help! :D

Is there a way to make JB Weld darker by adding something?

Kinda wish he would have roughed up the head mating surfaces a touch to increase mechanical adhesion.

He was here yesterday. Phone no. in his avatar.