Should all 8 primaries be about the same temp?
 

2006 8.1L running long tubes, Jet Hot coated.

Just got my truck running again and I am trying to ensure all 8 holes are firing. I fired up my truck and let it idle for a few mins. Using a laser Thermometer, and pointing the laser at the same spot'ish on each primary (about an inch off the flange as the primary bends downward) I get the following in degrees:
8-210 7- 240
6-260 5- 265
4-265 3-280
2-140 1-180

CYls 1 and 2 have me a little concerned. Should they be the same'ish temp? Logically they should be but i am wondering since they are the most exposed and closest to the fan, maybe they are being cooled?

thoughts?

Yes they should all be about the same.

The fan should affect them in a gradual fashion from front to rear, if at all; like, maybe 20° or something from one to the next behind it at the most.

I'd add #8 to your list of ill patients.

What do the spark plugs look like?

Copy. That makes sense. sigh.

I have brand new NGK Iridium 7164s set to .055. When I say "Brand new"; they have bout 10 mins of collective cranking (from troubleshooting) and about 2 mins of actual running. The injectors are also brand-new Fuel injector Clinic injectors. Not saying the plugs or injectors "can't be bad" but I am a little less suspect of them.

Coils are used factory coils from when I bought the engine on craigslist. I have a spare set of wires; maybe I will swap those 3 holes with the spare set and see if that makes a difference.

This is not a reliable method due to the coating unless you were certain the coating was the same exact thickness on all primaries. I think if you were having misfires on three holes 50% of the time, it would be obvious.

Fair enough, @BigKID . In my defense, I bought this engine used and it has almost always run terrible since I got it running. I have had a multitude of issues AND my tune is very immature. Compression is FANTASTIC all around so I know the long block is healthy, but the issues I have been fighting have hidden when a hole (or 3) goes limp. Each fix it gets a little better.

I also 100% understand that shiny coated headers are not "reliable" for tuning but I think they can be used, generally to see if a hole is firing.

I replaced the plug wires on 1 and 2 and that seems to have brought those 2 cylinders much closer (temp wise). Engine also seems to idle and rev a bit smoother. It is still not silky smooth like I would expect a mostly stock 8.1L to be but it is much better. Tonight, I will also replace 8's wire and see if there is a difference there. I also hope to go the first trip out and about so I can get some data for my tune.

I understand your logic and it is sound troubleshooting with bare headers. Just didn't want you chasing something that isn't there due to the inconsistency of the header coating.

When you say "runs terrible", can you elaborate? I presume this is a transplant into the '71? Majority of issues I have seen with swaps are on the electrical side where something went array with the wiring.

Rgr, I really appreciate it! This is the kind of stuff this forums exists for, right? I am NOT an expert, or even close so I will take any advice or questioning I can get.

Runs Terrible: when I VERY FIRST got it going, I had misfires. MANY misfires. it was so Pig rich and spitting black smoke. When I drove it the first time, the first 1/2 mile was bad, and it got worse as I drove and fouled the plugs. By the time I got home (about 1.25 miles total drive) it would barely idle. I also didn't realize I had the brake signal incorrectly wired so while I was driving, Terminator thought I had the brakes on the whole time. This meant it was limited to 10% throttle and first/ second gears only. AND the cam sensor was going which meant dirty plugs, sketchy wires, bad tune, and poor timing.

Brake switch was first fix. Truck came alive after that (as you can imagine). Tune update and better injectors helped with the pig rich part. New plugs helped. Sketchy wires helped a lot. I also found the passenger side coil harness was faulty. Replacing that made a HUGE difference. Imagine going from 3 cylinders to 6.5.

I learned a ton more about my tune AND I have a tuner helping me out. The tune is much better but not good so I have some dead spots but is finally driveble. After replacing the 2 spark plugs wires it runs pretty smooth but not super smooth and I still stink a little.

Yeah, this truck was originally an AMC 360/TH400. It is now an 8.1L from a 2004 Kodiak and 4L80 and BW 4101 xfer case from a 97 K3500. All the wiring on the truck have been replaced. Truck harness is Painless, engine is Holley. I am not saying that Like "Oh, I replaced all the wires and I am good now". I am saying it more like "I messed with every single circuit so wiring problems are ABSOLUTELY on the table".