Here's what I have-69 Charger 440 rebuilt in 93. Aprox.5k miles. 40 over, mild cam, stock manifolds, Edelbrock 750, electronic ignition. Several years ago Motor seemed to develop a slight variable miss at idle and under load. Still runs very well. Decided to chase now. Carb was rebuilt last year. It has NEW plugs, wires, distributor from Rick Erhenburg with cap/rotors, ECU box. Wiring and coil changed a few years back. Pretty sure I've ruled out anything electrical. Compression test showed nothing unusual. Vacuum gauge shows a very shaky needle at about 16 inches. Can't find any leaks. Doesn't smoke or burn oil. Note: I think this developed after I had a massive back fire. While i was getting off the highway my ECU box burned out and the car sputtered, stalled ,and backfired. Popped a new one in and continued on my way.
Any suggestions welcomed. Thank, M
I'm sure you'll get lots and lots of possible causes for the miss but, before you go shotgunning parts, I suggest you find a shop with a scope and let them diagnose it. You'll save money in the long run.
The shaky vacuum readings are a clue:
https://www.onallcylinders.com/2015/05/08/quick-tech-how-to-read-a-vacuum-gauge-to-pinpoint-engine-problems/
The parts I replaced ranged from10-25 years old so I figured start with the basics. The old distributor had quite a bit of play in the shaft bushing and I thought that was it. I do know something about vacuum gauges but find it hard to believe valve guides are shot with my millage.
Quote from: Working9 on June 30, 2022, 01:00:14 PM
I do know something about vacuum gauges but find it hard to believe valve guides are shot with my millage.
Why? Do you know what was done in 93? Unless you went to a high quality race shop for your head rebuilt, or proof that the guides were replaced, most shops only knurled the guides.