As others have said, ceramic coatings will help a great deal, and between piston oil cooling jets and various alloys, you can PROBABLY push EGT's a bit beyond 1250 for a short period of time without damaging anything. However, I've said before and I'll say again that in my VERY strong opinion, doing so is playing with fire...you might get away with it once or twice or maybe even more often, but that doesn't mean the pistons will remain as strong as they would otherwise have been, and CERTAINLY does not mean you aren't potentially risking catastrophic damage.
I've told this story before, but it bears repeating...my first diesel was a 1980 IH Scout with the cute lil' Nissan SD-33T turbo. A previous owner had installed a pyro and a boost gauge...and, one day shortly after buying it, I tried to climb a rather steep hill with it while towing a Chrysler LeBaron. I hadn't had a chance to learn all the intricacies of the engine, and while I had had experience with diesels, it was almost exclusively 2 stroke Detroits in marine applications, and I hadn't learned the importance of watching the pyro nor what the implications were. So, when I was trying to get up this hill with the pedal to the floor in 2nd gear and watching the pyro get up past 1300 F, I didn't think it was a big concern. When I got home that night, I decided to look it up...and was horrified to learn that a) the maximums were 1250 F for a pre-turbo mount and 1000 F for a post-turbo mount, and b) that my pyro thermocouple was mounted post-turbo
The engine ran okay, and I thought I had dodged a bullet...but, after about 6 months (during which I was very careful with the engine, having learned better), I started to notice a slight puffing from the road draft tube....and, over the course of the next year, the puffing got worse to the point where I was leaving a huge cloud of smoke and even got pulled over twice. I never did a post-mortem on the engine (the body was too badly rusted out; I sold it to a guy in Oregon who parted it out), but the best me and the Scout message forum I was a part of at the time could determine, that one overheat weakened either a piston or a ring bad enough that normal operation kept eating away at it until it finally cracked.
Moral of the story: Hot-******* aside, the recommended limits are there for a reason...feel free to disregard them if you so wish, but do so at your own risk and don't blame the engine
when it fails. OTOH, from an engineering perspective (if not a political perspective
), I tend to be very conservative...I've been left stranded on the side of the road too many times for my liking (which is why I go out of my way to avoid owning anything powered by gasoline
), so I'd rather err on the side of longevity than go hot-******* around and risk calling a towtruck at an inopportune time.
Why do I have the sickening suspicion that a certain someone on here's now going to make a point of pushing his EGT's as high as possible and proclaiming success after one or two runs before his engine blows up?