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I have had this miss under load for a while now and can’t figure it out. New plug wires, hei, rotor, most vacuum lines, carb rebuilt. It’s 81 with e4me . Idles great with no miss. Has good power. Under load it has a miss that sound like one cylinder. Checked rockers and movement so I don’t think wiped cam lobe. Took plugs out after about 500 miles. Not terrible but #3 has some build up. Any thoughts on what else to check? Next up is replacing wires again.
Did you route #5 and #7 as far away from each other as possible?. From leaving the dist cap, all the way to the plugs, they need to be apart.
Due to the firing order of Chevy, those two cylinders can interfere with each other's firing. Especially under load.
This is known as Crossfire Induction.
I should have said it had the miss even before I got the plugs and wires. I routed the wires separated thinking exactly what you said. Tried running in dark to see if arc and couldn’t see anything.
So, does it feel like an ignition miss? Or do you think it might be fuel?
Couple ignition things come to mind:
1) Distributor connector (make sure the connectors/wires aren't corroded
2) Coil conections/connectors are good. Ohm out the coil
3) Distributor cap and rotor (I know you changed these but..) 4) Distributor Pole Piece (see link below).
5) Probably worth ohming out the plugs just to check
The parts inside the distributor are exposed to high levels of Ozone, therefore parts can corrode inside it. I've had Pole Pieces crap out before. You need to pull the distributor and remove the shaft to look. There's probably a way to check before you remove it. The one in my 1989 pickup was completely corroded, the 'star piece' literally fell apart in my fingers when I touched it.
Make sure the engine is properly grounded and the computer too. A bad ground can cause issues. Back in the day, the old-timer mechanics would tell ya to take the car out to a dark place on a dark night (no moon) and pop the hood, look for errant spark plug wire sparks. And yep, you can see any sparks really well. https://www.corvettecentral.com/c3-6...e-piece-273004
Misfire under load
