I'm currently having a few problems with my Ute which is that its running really rough at higher rpm. The engine feels really strong at lower rpm and starts to pull but when the revs reach about 6000rpm the engine has some sort of miss and struggles to rev any higher. It seems to be really bad in 3rd and 4th gear, it still has a miss in 1st and 2nd occasionally but not as bad. I first thought it was electrical as I have replace the coil, points, condenser, HT leads, and spark plugs but it still remains so now I'm thinking its the carbs (twin dellortos) and is a fuel related problem, I've checked the float levels fuel pump, fuel pressure (set about 2.5psi).Do carbs need re-jetting over time to suit the motor as its done about 9000ks since rebuild. I was also wondering if a vacuum leak would cause this?

Any help we be appreciated.

could it be valve bounce at higher revs? just a guess cause i drove a ute today and as it hit 6000rpm it hit valve bounce n sounded pretty bad and rough. my old man says the valves would just need replacing with heavy duty items if we wanted to rev past 6. which we all do.....

I would say air leak.
When I was in high school I had a V8 valiant coupe. I put a holley on it, but made a cock up with the adapter plate. It used to leak air, and it went fine untill it hit 78 miles an hour. Then it used to die like it had hit the speed cut out on a jap import.
Man it used to drive me NUTS! Just when things were starting to get interesting, BAM, it would die. It would sit at 77 miles an hour all day though.

If it sounds like an air leak then, are there any tricks on finding the leak?