Got a 1200cc VW powered Druine Turbulent up to 10k. Took a long time, took longer to get down, pulled off the power - cyl. hd. temp disappeared off the clock - can't do that, restored some power and temperature and stuffed the nose down - Vne 104 kts. cyl. hd. temp. also disappeared. Eventually came down with some power and speed to retain some positive cyl hd. temp.