Valve Float?

[Ieatcamaros]

Me an my brother were riding around tonight in my 89 351 stang. We were recording some video clips to submit to mustang exhaust.com. Anyway, I just got this car back on the road last week. I had rebuilt the tranny and put in the 4.10 gears. Tonight is the first time either of us have gotten on it (past 4 grand). It has a small cam in it. It only yields .488 lift with the stock 1.6 rocker. The heads are D0OE with 1.84/1.54 valves. They had a valve job done last winter. I have submitted a video of him driving. You can listen real close and hear the flat spot he hit in third gear. I am not sure if it is float or not cause it doesn't really fall on it's face, it just quits pulling and wants to hang there around 5200-5500. The needle jumps in that range. It kinda scared him after that 3 seconds and he went ahead and hit 4th. In my other car(the 89 302) it has a F cam and the e7's. It floats like a mofo at 5500. The float in the 351 car is not near what the 302 car is. Like I said, it just quits pulling. I am not sure what it is, so I ask you all. The ignition timing is set dead on 10degrees. If I remember correctly, the duration is 280/280.