Cruise Seems Lean

71GSSDemon said

I am trying to determine if it was outside temp, engine temp, combination of temps, lean mix, etc. If his car ran so much cooler than mine, like Yellow Rose commented on, maybe it is a big factor in the equation. It was a gear change, cruise rpm change, highest ambient temp ever driven, and furthest I have ever driven it.

I pulled the plugs. They don't look good but not as lean as originally looked. There is oil burn present also

Click to expand...

What is the "it"? The hesitation and/or the surge? I think we know that is most likely due to the increased load on the engine.
If the gears hadn't been changed coolant may have run a little hotter strictly due to the length of time running on a hot day, but none of the drivability issues would have shown up. Did the gear change also increase the heat load? Possibly, if the engine is working harder.

However, now seeing those plugs, that could cause some drivabilty issues right there. I don't know if its just oil, or oil plus kernel growth and flame front being disrupted. Look at number 6 and the one location on the end of the shell thats pretty clean is where there electrodes don't shadow.

Over in the thread discussing gasoline I posted some distilation curves. Today's pump gas is a little more difficult to prepare properly in the chamber for good steady flame growth from the kernal. I would take a look at the factory spark plug for that head. Then if you don't want to use Champion, find a cross reference to whatever you prefer. If you do use the Champions - just check each one visually - that's what I've been doing. Consider them expendable. Use a set for long interstate run, and then see what they look like.