Well dang, hadn't thought of it that way. I guess the flip side is - when the fan is not running, the air flow through might be better. The holey shroud theory is probably right up there with those people who swap out a 190° thermostat for a 180° unit thinking it'll run cooler. The thermostat opens sooner but max cooling is not improved.
Oddly enough, the only time my temp light ever came on was when I was on the freeway - doing about 70mph, slightly down hill so not at full throttle. I think the stock fueling is lean at less than full throttle. On the other hand, I've pulled long inclines WFO and the temp stayed in the good range. I have one of those cheesy radiator cap thermometers to help me worry about engine temp.
Originally Posted by pfy50
I am thinking that the Mod is feeling the extra heat because it is in fact damaging the efficiency of the fan to pull air away from the rear of the radiator. The purpose of the shroud is to direct the air& heat coming thru the radiator to the fan for removal effectively. If you put holes in the shroud it no longer is working as designed. To move more heat away from the engine you make the radiator larger, the fan larger or the same fan faster, or some combination of those three.