High Speed Mis

[rocco]

A friend of my as a Stingray with the 454 motor...we have been working on getting this mis out for about 4 months now..Heres the problem??
Starts good,,,,Idles good,,,Runs great up to about 4200 rpms,Then it starts to cut out,popping and cracking pretty BAD....sometimes it quits..Then it starts right back up....WE have,,,,Replaced the plugs,,,Wires,, Dist cap,,,rotor button,,,coil,,,fuel Pump,,even by passed the gas tank for cleaner gas......Electric box.....New plugs again,even coil.
Sprayed Carb Cleaner while running at that speed..,,Have'nt replaced the Carb yet,,,,Still wondering about that?????All new Gas lines too...
Any Ideals..................Thanks Rocco

[Daryl]

just because you don't mention it - have you made sure the points are set correctly and in good shape? or - have you put in an electronic conversion? maybe you should.

[skinautique]

make sure the points are set correctly and make sure that you didn't cross any plug wires and also make sure that the plugs are gapped correctly.

[rocco]

High speed mis

There are no points,,,,Plugs are gaped right too...wires are right also.

[882001]

is the mechanical or vacume advance working?

[Rick]

check the timing.

[rocco]

high speed mis

NO,,have'nt check the timing yet,,But how could that be,,,Because its starts great,,and runs great up to 4200rpms,,Idles smooth too..
All plug are the correct gap,,and the wires are right too....We are thinking on getting a New Carb next........

[Rick]

If the timing is off the advance at high speed would advance the timing beyond the cylinder that is supposed to fire to the next one. At high speed the advance is supposed to be 30-35 degrees from 5 degrees. If it is at 15 degrees at idle the boat will still run but the advance is now to 50 degrees at high speed.