PER General Motors, 1450 degrees EGT for up to 5 minutes, without serious damage, spikes care ok, due to the fact that the constant heat soak from high egts will not be able to penetrate the steel and alumium inside the engine. Running 1400 degrees is able to be done for unlimited. I got that from a buddy of mine who works for a local GM dealership, it's from his technical service bulliton. I run 8-900 constant driving around birmingham, al. where it is hilly. but if i get on it when im drag-racing or sled pulling i easily hit 1400-1450. but that's PPE hot ET +2 with stage 2 turbo, injectors, and a ton more addon's. i wouldnt be worried, but i wouldnt do it every day.