National Records

[oldskool]

Here's another dummy question. And the only reason I'm asking is because I don't know the answer and would like to.

I see that at most big races there are cars running under the national record for their class. So my question is: why do they choose not to run for the record ?

I could only think of two possible reasons. Either they don't want to go thru an additional teardown. Or they don't want to call any extra attention to their combo, which might result in a hp refactor.

So can some of you guys clear this up for me ?

Also, I've noticed that some cars are going about 2 sec quicker than the same combo did back in the 70's. Is there any way to look up what the record was for a particular class, say in 1975, and what car held that record ? Or how about a list of when that record was reset, and by what car ? Or is this kind of info just too detailed to keep up with and have available online ?