As I am rebuilding another T engine I am wondering if it would be advisable to drill a second oil hole for the center main.
It would seem to me it would benefit from splashed oil from both number two and number three rods.
Right now it is a bare block, now is the time to do it.
I did that one both of my cars. One thirty years ago and the other twenty years ago.
Two is fine, they were drilled like that on the later blocks.
The first fifteen million got along without a second hole. FWIW.
I've only come across 2 holes in pre Canadian veteran blocks, from then on, only 1 hole in Canadian blocks.
Ford made two oil holes in the center bearing until 1914. The start of only one hole was at August 26, 1914: http://www.mtfca.com/encyclo/doc14.htm
To get a feel for how long time it could take from a change in the drawing until actual change in production, here's an example - the engine block drawing change was recorded 07-18-14: http://www.mtfca.com/encyclo/E.htm#eng2
This was a cost cutting change - Ford didn't find any significant change with only one hole, but he never intended his cars to last more than 100 years, more like five years, so since I have the time to do stuff like that when overhauling, I did drill an extra hole on both my engines and do benefit from a better oil flow to my center mains without any ill effects.