Thanks for the reply. Good to know that it's just a noise I can ignore, unless of course it gets really loud. I will try that weight oil to see if it gets quieter. Would 20w50 be too heavy? Also, do I need to use ZDDP additive in these engines? Thanks again.
Motor oil already has zddp in it, just in lower percentages than in the past. I would only use a zddp additive in an engine that has flat tappet lifters. My thunderbird has flat tappets and I use Comp Cams break-in additive in the oil. I could be wrong, but I believe the 4100 has hydraulic roller lifters like the rest of the 4.x series..
Wow I would not have thought that any engine made in the 80's would have flat tappets! What a dinosoar... This is what i use in my Thunderbird which is 15 years older and has hydraulic flat tappet lifters: http://www.summitracing.com/parts/CCA-159/