Anyone know what would cause part of ground strap to break off like this? Was running rough and 2 of them were like this. No evidence of melting or detonation. If anything too rich... Hopefully pieces shot right out the exhaust....
The broken ones were black due to missfire. Others look tan color. 100 or so passes on them. Could the wide gap cause stress on the plugs? I run .050
Only if the gap were wide enough to cause the electrode to contact the piston. (very unlikely, but not unpossible) Can you -scope the top of the piston? Even with the piece bouncing around in there dinging up the top before it (hopefully shot out the tailpipe), you should see a distinct impact mark on both pistons in the same location and depth.
AC 42XLS...cold plug and only running 34 retarding to 30 at 5000 rpm Doesn't look melted. I'm thinking need to index plugs maybe 700 passes have loosened things up and piston going higher? Looked with scope and piece bounced around, dings on piston.....before it exited.
That plug crosses to and ngk 7333 heat range 6. I run ngk 7173 on our motor with al heads, it's a heat range 8. That's 2 ranges colder I'm guessing to get the gap to .050 gap you had to open that up about .020ish. Which really shouldn't hurt anything. The ones I run come in around .031 and I open them to .045
My theory is that when I gapped them a stress crack formed and then later it broke off.... Years ago I had NGKs break off at the weld of the ground electrode so I tried to not be as aggressive gapping them. Maybe I need to invest in a really good gapping tool....
Think I found the problem....rotor button in distributor cap was completely worn away and rotor was running on surrounding metal...lots of evidence of spark scatter. I guess it's good to have a motor last long enough to wear distributor cap out!
Maybe so....I can't believe it ran a 10.30 129 at US13 on Friday....missing.... I lose track of how long it has been on parts but that cap and rotor has prob been on the motor since mid 90s.....
MSD's usually eventually eat the rotor button in the distributor cap. Every so often, I take the cap off and eyeball it.
It's cheap insurance I replace my cap rotors and wires about every 3 years and I dont put that many runs a year on
I had the same thing happen last weekend at the track I'm testing this methanol water injection and had two big backfires and broke a plug and a few of the other plugs the gap was almost gone.
