Burned valve causing hotter temps? Options

[ThePaintedMan]

Hello all,
While I continue to save money to have a set of heads rebuilt, I'm still trying to pick up more information on whats involved with a top-end rebuild, but also learning how these engines work conceptually.

Something I've been curious about - a friend and I drove 8.5 hours to and from Braselton two weekends ago for Petit Le Mans in the 914 and we dealt with engine temps the whole way. Granted, the VDO CHT is largely inaccurate, but I've at least come to understand that its usually reading around 10-15 degrees below what the actual temps are. Essentially, we could not keep the thing below 350-375 degrees at any point along the way, either during the day in Florida when the ambient was 85-90 or at night in GA when the ambient was in the low 50s. At around 65-70 MPH the car is turning 3,200-3,400 RPMs in 5th, but it seems like it just will not stay cool, at least at that throttle position. Otherwise, the car is tuned well and the carbs are synched. I have suspected a burned ex. valve on #3 for awhile, as this is the only mixture screw that doesn't seem to have much effect on idle. The paper towel over the exhaust trick also confirmed that it is "sucking."
My question is, could a burned valve, which is no longer seating fully, also be the reason why CHTs are higher for that cylinder? Since the contact between the valve and seat is responsible for soaking up a lot of heat (somewhere around 20-30%) in the head and dissipating it, wouldn't a burned valve negatively influence this?


Thanks for humoring my nerdy questions!
-George