Well lets look at it this way:

6:00 am - arrive
7:00 am - Clear customs, pick up luggage etc, and be outside the airport (it wont necessarily take an hour, but this hypothetically speaking).
8:00 am - Arrive at Pyramids

You'll probably be able to spend half an hour though, you have to be back for check-in 2 hours before your flight right?

8:30 am - leave pyramids
9:00 - 9:30 am - arrive at airport.

It may be done, but very risky. If only you had one more hour!