High rpm miss identified
 

Finally!. I've been searching for a high rpm miss for a while now. (5000 rpm and up)I replaced my MSD box, coil, cap and rotor, Tach, plugs.even checked the volts at the MSD box while making a pass by hard wiring in my volt meter and setting it in a place visible while driving. As a last ditch I figured I would put my MSD distributor back in and unhook the crank trigger. That solved it. I was confident it wouldn't because it's fairly new. But from what I could tell on a very limited hard 2nd gear pull it fixed the problem. Now I have to evaluate if I will replace the mag pick up or just leave in the distributor. It has locked timing so I'm not worried about the timing bouncing around with it over the crank trigger.

That's good you found the problem component. Have you tried to diagnose why the crank trigger is causing the issue? It will probably take some digging. But a crank trigger is nice to have. Hopefully you can find the root cause and get it working reliably again. Check the simple stuff first. Loose magnet, loose or internally damaged wires(test continuity from one end to the other), loose sensor bracket, etc. Could possibly be phasing, since it shows up at higher rpms. Could be rfi. Good luck with it.

Its amazing what G force will do, anything slightly loose for wiring will move.

I'll check the continuity on the wiring, not sure about RFI. Never thought about that

Well, i can imagine a crank trigger pickup vibrating around. Was the pickup able to vibrate?

The road race Post put blame on an HEI assy with locked ADV. I'm curious to what item within the HEI caused the grief?

Road race HEI issue was some kind of harmonic issue with weights, springs and end play. It was not locked out. Also driving an 80 lb. oil pump. Something in the interface between these parts was not happy. Concerning OP's crank trigger, as mentioned, the trigger wires are a twisted pair. One of the very few issues I have had with MSD stuff has been the two wire connector male and female. I have had an intermittent connection there. They are not soldered by MSD. I remove the 4 terminals from the connectors and solder them at the crimps. Then after plugging them back together, wrap the connector with a little electrical tape. Run that twisted pair away from secondary ignition, electric cooling fans and any other high draw devices. Not really much top go wrong with the mag pick-up. I have noticed quite a bit of runnout on the trigger wheel in some applications. Check the MINIMUM clearance in 6-8 places around the wheel between the magnet. Make sure the closest gap and the farthest gap is within the specs. If I remember right .050-.070? Check that and if in doubt, stay on the minimum end of the specs.

Agree with Scott65, Rotor phasing!

The bracket and pick up are still mounted solid. I had the gap set at .050. the wires do run under the intake along with the hot wire to the alternator, but has been like that since I put it together. This started a long time after initial start up and several trips to the track. Could be some kind of interference with the wiring. As for rotor phasing, I checked multiple times to make sure the rotor was at #1 when the timing was at 34* on the balancer.

Even if rfi isn't causing the current issue, I'd keep those wires way away from the alternator wiring. That stuffs noisy as he##.
ETA: shielding is an option, grounded only on one end.

Check your alternator for AC voltage. An alternator diode set can slowly fail allowing AC voltage to pass. This causes interference issues like radio whining.

Rotor phasing is the big deal done by pointing the timing light at Post #6 with a hole in a test Cap, rotor-at- 6 during the flash vs RPM is a comforting good result that will provide a good night sleep, and clean hard acceleration.

Shielded wiring on that circuit is a great idea. Routing close to a water pump motor can cause a issue also.

Remove the belt on the alternator for one pass with the crank trigger installed. If it is noise, you may be able to arrest the noise with a capacitor.

Currently I have both the main wore for the alternator and the wires for the crank trigger running under the manifold on the valley cover. Would it be separated enough to run them on opposite sides if the intake? Is that enough distance?

I was able to get by with the alternator wires under the intake and the crank trigger wires running along the junction of the intake and valve cover. But my crank trigger wires are shielded.

I had a high RPM miss while on the transbrake (and thereafter) ... turned out being a bad crank trigger sensor, an MSD unit .... I would shotgun the sensor out of there and see if it fixes it, especially if it was running fine and then started to degrade.

Did you find the issue? Curious because I was just recently chasing this exact issue but it would randomly miss, other times run clean. I threw the kitchen sink at this thing (new fuel pump, regulator, coil, switched my pick-up wires to the shielded wire, etc).

After 3 weeks of trying to figure this thing out, it turned out my distributor bearing had come apart and caused the rotor to not spin true. I noticed my cap had scuff marks from the rotor making contact to it which made me tear it apart and holy S#... the bearing was completely trashed. Popped a new one in Sunday morning and it ran clean.

always carry a spare crank sensor --- they will drive you nuts