Originally Posted by Bubzilla:
My observations are that it would be a track that you're constantly on and off the throttle, not one that you run flat out the whole lap. Most motors I've seen start to blow up get hurt initially due to the sudden RPM changes.
The ever changing stresses and harmonics with varying the engine RPM's is extremely hard on the rods, rollers, and piston wrist pin areas, not to mention the cam gear drive backlash lag on deceleration offering the valves an opportunity to kiss the piston a few times.
I agree with what he said but to add, its multiple sudden RPM changes while under
heavy load that is tough on engines.
Even 3/8th banked dirt tracks when tacky, can be killer on engines. When guys back them in hard, the engine is under extreme load trying to pull the car out of the corner considering the moisture in the track and how hard the driver threw it in there. This happens twice a lap, over and over again in a short amount of time.
Its the same reasoning why when you watch a Nascar race at Martinsville, they say time and time again its one of the toughest tracks on engines, yet one of the smallest tracks. Many more engine probs at Martinsville than Daytona usually.
You might say, well, if that on/off the throttle theory is correct, then why wasnt the old Kokomo, when it was dry slick, an engine killer becuase drivers are really playing with the throttle there. Its because that situation is totally different, they arent putting much of a load on the engine in that situation.
I could be wrong here, as its been a good while since I worked on engines but...