Have you checked the voltage at the coil while it’s running?
Checked voltage on the hot side of the resistor, and compared that vs the voltage at the battery?
Many years ago on my heap, I put in a higher rpm motor than I had run previously, which allowed some ign issuers to show up.
In my case I had lots of loss through the old factory wiring.
I peeled off some of the insulation in several spots and it was all green inside.
That’s when I went to a MSD 6A box...... since the power feed wires go direct to the battery, bypassing all the factory wiring........ and getting rid of the ballast.
I used the big yellow Accel Super Coil with it, which was already used when I got the car in 1981.
That being said, in my mind, it’s just as likely a valvetrain issue as ignition.
The pitfalls of fast rate hyd cams:
https://www.hotrod.com/articles/mopp-0510-440-engine-dyno-test/ E Street 75 cc Heads - Angled Plugs
Came across this article and started with the spark plugs - They talked about toasted boots on #6 plus #8 later in the article
http://www.moparts.org/Tech/Archive/bb/Lobe.htmlNever noticed anything on the plugs themselves or the spark plug boots for that matter , but once I looked inside the boots on #6 and #8
They where black - Went to pull the plug boots off and the metal terminals came with them
Serious heat issue and misfire with these two plug wires
Two new plug wires and those 1200 degree boot protectors , and I was off thinking for sure this was the issue - Fixed on the first day
Man what a difference overall , Smooth , Rpms come up fast , really fast , first gear all the way up to 5500 5600 Rpms shift into second
Engine feels Awesome , like I gained fifty horse overall
Second now coming up to 5200 5400 Rpms and it starts sputtering , PINGING like crazy
Cruise mode on the highway 3200 Rpms at 70 mph in Drive - Get in the gas to 5500 Rpms no problem
All day long in first to 5500 5600 Rpms then
Verified fuel pressure with gauge taped to my windshield - 4 to 5 psi at full throttle - Delphi mechanical stock 383 , verified pump rod at 3.22 “ factory original from 1971
Friends gave me a couple different ECUs and a new coil - Pertronix 40011 Coil - Jumped the ballast resistor
Idle 700 Rpms 13.5 volts to both sides of ballast , 13.5 volts positive side of coil - All wiring is fairly new and looks great
Volts come up to 14.5 with Rpms
Different ECUs no change
Obviously there is a huge difference between fuel pressure and fuel volume correct ?
I also pulled the valve covers - I wanted to check my rocker arm geometry and wear pattern with these Sealed Power rocker arms and shafts
Man I couldn’t bee happier - Rocker arms , comp cams push rods , spring retainers no rubbing , valve stems looked damn near perfect brand new after two summers
That’s where I am at - A much better running engine overall , all day long out of the hole in first to 5500 5600 , then falling off in second around 5200 5400 on a full run and PINGING like crazy
Thanx Fast 68 Plymouth for all your help
