12SI 75 amps. Engine 305 v8. I just used my infrared temp unit & checked temp on alternator. Read 160 *F. Is that excessively high?

Just had alternator rebuilt a month ago.. Squabbling with the rebuilder shortly after the rebuild because it dropped from near 15 V to 13.1 V with headlights on after 60 miles. Continued driving as alt was charging.
He says it is not the alternator rebuild but he ran into a similar problem with a customer. Battery in subject was car good & load tested. He connected one of his rebuilt units & same results. . Turned out the battery was defective. new battery & problem resolved. ??

 

Seems reasonable, depending on the load, underhood temp, etc.

 

Of course It's gonna get hot. Those exhaust manifolds emit tons of heat, and heat rises.
The alternator mounts with a bolt going through and into a cylinder head. It's HOT under there...

 

I may have solved my problem.
I added a ground strap from engine to chassis to see if that would make a difference (I had to do in my 1972 Buick GS way back as it was missing)
Here are the volt readings at various times in my 20 mile run.
1) engine off = 12.66 lights off
2) at idle = 14.6 lights off
3) after a few miles = 14.6 lights off
4) lights on = 14.36 & alt temp = 160 tops
5) after 20 miles on the road at various speeds back at home = 14.36 alt temp 160 tops
My next out of town long run is in a couple weeks, so I will cross my fingers & hope problem is solved!