911 distributor

My 914/6 has just been rebuilt with S cams and E pistons/heads. The engine runs OK, but at mid to high rpm will spit back through the carbs and misses alot even when hot. I suspect the old Mirelli dist. is worn. I have three of them but I don't know if any are really good. Can anyone suggest what I might do? Does Pelicanparts have a source for a Bosch distrib. that would be better suited to the S cams and E pistons?

It sounds to me like you need to determine whether your problem is spark or fuel...Don't assume anything at this point...Start with ignition...check voltage at alternator(13-14v)...check coil wire and coil...distributor cap and rotor (cheap enough to replace)...using timing light, you can check advance of distributor...check resistance of spark plug wires...Are you getting fire to plugs? I run hot NGK's (I think they're 5's). If all checks out, problem is in carbs...can you determine which cylinder is missing? Troubleshoot carbs the same way you did ignition, start with fuel pressure...Are intakes leaking air? Are throttle plates properly aligned...float levels ok? Accelerator pump volumes ok? Linkage set properly? Webers can be off a great deal in the jetting and still run without missing...Does the motor seem to be running rich or lean? Auxillary venturis ok? As I have a very similiar setup, I will be glad to answer any questions you might have (if I can), You can e-mail directly at smic@gate.net...Remember, these type of problems can be elusive, but I'm sure you will find something simple. Good Hunting,
Sean
75 911s (with euro RS motor, Webers)