I was playing around with the company's new FLIR cam with my dune buggy after idling for 10min or so and I immediately noticed something interesting. About a 100 degree temperature gradient between the front and rear cylinders on the exhaust for both sides!





It will be interesting to see if the dual carb setup I have coming has an affect on this. If not I'll do some more digging but it's interesting nonetheless.

going to need hotter or colder plugs for the front or rear.  which ever way you want to take it

That is most likely due to the single 2-barrel carb and the firing order, happens with dual 1-barrel carbs like the 34 Weber I have on my DD.  The firing order is 1-4-3-2, so the even number cylinders(rear/hot) are fired before the odd number(front/cold).  What happens is the even number cylinder starts to pull air through the carb but not enough for a full charge of fuel so it fires lean if at all.  The next cylinder to fire is the odd number on the same side, and it gets a full charge of fuel from the airflow off the pressure cylinders, fires properly and the process then starts over on the other side of the engine.  Again this is common for VW's and any form of sharing 1 carb barrel between 2 cylinders be it a single 2-barrel and dual 1-barrel carbs but it happens only at idle, as soon as the throttle is cracked the engine runs normally on all 4 cylinders.  Assuming the car is tuned properly, if you go drive it around all the pipes will be at about the same temps.

Spark plug heat range has nothing to do with this issue. This is due to the one cylinder running leaner (hotter) than the other.