My 240z falls on its face in 4th past 5000rpm, help!

[ZcarsRock]

Here is what happend to me. My friend and i are driving home from drill along an open stretch of Old 40. He has a 2002 Mustang and i'm in my Z of course. We are just kind of cruising, and i'm behind him. He opens up his car, so i attempt to keep up. I notice as i accelerate the car is smooth till about 4800 to 5000 rpms. Then it happens!!!! Same accelarator position and the tach goes back down to about 4600rpms. I floor it and the rpm slowly climbs to about 5300rpms and wont go beyond this. What is my likely problem? Vacuum leak? bad Gasket? improperly set carbs? I have to large round SU's. Thanks for your help in advance.

Tony

ZCarsRock!!!

[Ed]

Check your ignition timing. Sounds like it might be off a bit. Also check the condition of your points. It might be time for a tune-up.

[2ManyZs]

Could be a fuel starvation problem, ignition problem (timing or advance) or it could be your valve springs are soft and the valves are floating. :cross-eye

Check your timing, points, vacuum advance etc, then go to the fuel side if the problem persists. If neither helps, it may be time for a valve job and springs.

[smg1404]

Also don't forget to check your plugs... You may need a colder heat range.. If they are a hot range, they may heat foul under high load conditions. This is probably not your problem, but it is worth checking. Also check the fuel filter, and air filter.

[smg1404]

I thought about this ... and assuming that the car could reach higher rpm before. the problem could easily be point gap, as I think someone else already stated... If the point gap becomes too small you will not allow enough time for the coil to saturate... Check the dwell... I have found that to be the most accurate way to set points... throw your feeler gauge away for points... Use for the valves though... Just a thought.