This cap was on a 455 that previous owner installed a Pertronix on. Car ran ok but seemed like something wasn’t right. Pulled the cap and found this? Threw another cap I had on and runs a bit better. Anyway, looks like the center “button” just cracked and broke off and the top contact on the rotor was getting into the brass.
Several things can cause that. 1. Ground issue. That button becomes the high resistance point as current flow from the coil to the button, to rotor to conductor posts, to wires, plugs, heads, block and ground back to battery. If the grounding/bonding along that path are not adequate, the button will overheat, (even more resistance) and burn, as it is also the least able to deal with the energy. 2. Insufficient contact of rotor cap and button, or a gap (coil to cap pathing, above). 3. High resistance wires, or inadequate connection of wires at cap and or plugs. 4. Defect in the button and broke off. (bonded type) Some buttons (like a bullet with a spring) are solid brass, some are solid carbon and some are a small carbon "pill" bonded to the brass rod. Grounds/bonds are such an important part of the electrical system and seem to be most overlooked in troubleshooting. (Careers in Aircraft maintenance, electronics and computer systems drilled that into my brain...). Hope that helps.
That’s great info. It has Taylor Spiro Pro 8mm wires on it. I guess I’m not sure if those are high resistance or not.
I had the Taylor 8.2mm Thundervolt wires on my 68 Skylark. (430 build) They are very low resistance and I had issues with bad miss and very bad stumbling it partial and WOT. (Car ran like manual choke full on). (Great Wall of China text alert... Y'all been warned) After chasing several issues (new build so lots of variables, including EFI), I had replaced several components in eliminating variables. After I had it running better, (temp installed new MSD wires), I tried reconnecting the Taylor wires, and the car seemed to run fine. The last thing I had changed that seemed to make the greatest difference was the O2 sensor, so I figured that was the culprit and started reversing the other changes to see if the problem returned or not. Drove the car about 30 miles at highway speed, around town and then back home. Next day another 30 miles, and stopped at a drive through, idling for about 15 minutes, then headed back home and the car just started laying down again, and I could not get it past 70MPH on flat road, watched AFR and TPS. AFR was reading 13.8-14.3 while TPS was 30s-40s and used 1/4 tank in 20 miles. Pulled random plugs and they were rich fouled (heavy soot), so I pulled the O2 and it was fouled also. I pulled the wires and put the new MSD wires back on, fired up the car and took it out, and the problem cleared in about 1 mile on highway. So, my conclusion (so far) is the wires were the issue, and just took time for the poorly firing plugs to foul, and during this time, the AFR and O2 readings are "false" and the EFI is sensing "lean" from the unburned fuel/air raising O2, so the EFI is adding fuel, the AFR "reads" near normal, even though it is not, and over rich fouls plugs, poor burning and it simply starts laying down, (hence the "full on manual choke" experience). I am manually tuning the EFI, as it does not seem to want to self learn correctly or fast enough. However, it is running better and not fouling plugs or the O2 with the MSD wires. I did Ohm both the MSD and the Taylors, and the Taylors still Ohm very low resistance, so they did not break down nor are they out of spec. And to be fair, (not wanting to trash Taylor, if it is something else) I have seen anomalies that will plague one build and no other, all things being the same. Makes my brain feel like it is rubbing a cat's fur backwards, and go against all logic and understanding. I still do not have the car running as it should, but wanted to address your concern about the Taylor wires. Are they the problem (for me)? I am not 100% certain, but they are a big contributor. Once I get the EFI tuned better over the whole range, I will know more. I also ran Taylor wires on my Nailhead, (my 64 Skylark) and changed them (it was aesthetic/color reasons), but I also noticed it ran better. Also running 2x4 EFI, so cars are similar in a lot of respects. Since this was a year before the 68 was put together, I only thought about it after swapping the wires back and having an issue, that there may be something to the Taylors and this EFI system, but again, no real empirical science, just "gut" and experience. All of this has been relatively recent. Less than 800 miles on complete driveline, counting break in of 500 miles on a new rear-end and short heat cycle drives, then a transmission failure and rebuild (converter damaged in shipping), so EFI never tuned correctly, and for the most part, I am starting from the beginning on the running issue. Just got the car back together and "sort of solved" the poor running in time to drag the bad acting step child to the GN Nats. Now that I am back home, I'll be beating this stepchild and getting her to behave. Gonna name her "Nancy" and then beat her like "Tonya". Where's that big hammer...?
I just this minute got back from an actual test drive since that cap was replaced and it’s much better on the road. Gonna drive it for a while and “test and tune” as needed. Just getting this car on the road after buying it from someone that did a bunch of work on it and let it sit. I appreciate the input though, real world experiences help more than anything.
