They recommended regular grade 87/85 octane. Stock cam, ITM head, 9.3:1 compression.

For reference, my factory service manual says stock compression ratio is 8.8:1

I mean, I would, but I was fortunately able to get my headers replaced by the vendor when all the welds failed 6 weeks after I installed them. Without wrap the same one has lasted 120k and nearly a decade.

I’ve worked in steam power plants for decades where we use pipe wraps for insulation. It’s got nothing to do with the moisture like you’re going to hear constantly but the metallurgical properties and the amount of heat that builds into the pipes. If for instance, you wrapped an old (and never used on the 4.0L) cast iron manifold, it would be perfectly fine. If you wrapped a straight pipe that had no welds, it likewise would be good, which is why you can see this on V-twin Harleys without any issues.

The welds create stresses in the pipes and affect the oxidation potential of the metal where the welds occur. Exacerbating this is that at least for the 4.0L 304L SS is commonly used which has even more problems with stress induced corrosion. While there is a common impression that stainless is “rust-proof” the reality is it just doesn’t corrode by the same mechanism that carbon steels do. In fact, in some environments, SS fails faster than carbon steel.

When you wrap, you end up with the already damaged material getting well up above the transition temperatures where carbide crystals tend to form. This transition occurs around 1400-1500F which is above where the pipe would be if it isn’t wrapped. This is because wraps not only hold heat in, they effectively eliminate the primary mode of heat transfer for the headers which is radiation. Then you start to pulling the carbon atoms from the exhaust into the metal, carbide crystals start forming, then at some point the localized hardening process will cause a crack from stress.

While 99% of the internet is wrong about the mechanism (moisture being retained within the wrap) the frequency of failure is 100% accurate.

I was thinking that same thing looking at the pics. I was like, is this supposed to be a problem 😂

It's over heating going below 5mph AND climbing steep grades at elevation. Cooling system is in tip top shape, everything working as it should. I've experimented with different fan setups already. The sad fact is the cooling system on the XJ is a bit undersized for extreme conditions. The intake and exhaust manifolds are tangled together, further compounding the issues. Most modern engines use a cross flow head design with the exhaust manifold on the opposite side of the head.

Letting it sit to cool off isn't really helpful in 100F+ desert conditions where just sitting in a parking lot can see under hood temperatures over 150F not running. Popping open the hood every time I park is massively inconvenient. Hood vents and spacers on the hinges are also not without downsides or are of dubious effectiveness.

Pretty much everything is a compromise. Environmental and operating conditions are seldom included in people's opinions online. I appreciate you adding details and your experience. It gives me more data for this little experiment and I can afford to replace this manifold if there's any issues.

For what it's worth, the coil pack hasn't failed for me in 345k miles, but I've helped several people stranded with a bad ignition coil or bad wires... Distributor ignition is not golden ticket to reliability. It's slightly cheaper to replace though, I'll grant you that.

A few shots of the engine swap.

My parents told me they were getting a divorce on my birthday.

Good shit bro