Wally,
I've made quite a few changes to the diverters on the alternator cap but I can't seem to get the temps on 3-4 to drop anymore, 3-4 are still about 40 degF higher than 1, and 2 is about 25 degF higher than 1.
I am going to try the T1 under cylinder tins now, but still wonder why #1 runs so cool with the T4 tins ... can't get it above 325 degF no matter how hard I try.
#1 has a nice airflow path from the alternator ring ... almost a direct shot of air to the head. Perhaps the diverters are directing the air to the cylinders and not the head on the 3-4 side
I will try the T1 tins first and then try your method of the horizontal plate over the cylinder bank as the airflow may be having a hard time getting past the first fin on the head towards the case. It is much taller than the last cylinder fin towoards the head and perhaps this is an airflow barrier.
More testing !
Sandeep