Cracked #3 Spark Plug
Thread Starter
Burning Brakes
Joined: Oct 2017
Posts: 1,230
Likes: 467
From: Colorado
Cracked #3 Spark Plug
I have a 2016 Z51, of which, I added headers, heads/cam, TB, e85. According to my gauges, I'm not running hot; however, I suspect the headers might run hot. During a non-spirited drive, I had a CEL and the car ran like crap, but not running hot (only about 60-65F outside). I drove directly to the dealership for diagnosis and repair. They are familiar with all my mods and my powertrain warranty is dead, so, out of pocket.
I expected a long diagnosis; however, within an hour, I had a cause and repair: #3 spark plug porcelain cracked and arc'd the wire. Replaced the spark plug and wire, and it runs like a champ. My question: what causes a the porcelain on the spark plug to crack (besides torque)? Is it heat? Too close to the headers? I've done these similar mod on other GMs (trucks) and have never seen this.
I expected a long diagnosis; however, within an hour, I had a cause and repair: #3 spark plug porcelain cracked and arc'd the wire. Replaced the spark plug and wire, and it runs like a champ. My question: what causes a the porcelain on the spark plug to crack (besides torque)? Is it heat? Too close to the headers? I've done these similar mod on other GMs (trucks) and have never seen this.
Melting Slicks
Joined: Aug 2004
Posts: 2,338
Likes: 482
My first thought is that a small fracture may have happened when installing the headers. Either by not taking the plugs out when installing them and unknowingly catching one or when removing them to install the headers. Typically whenever I install headers I always remove the plugs and suggest to the customer that I install new ones since I will have them out.
Safety Car
Joined: Mar 2004
Posts: 4,048
Likes: 1,476
From: South Florida
Heat won't crack porcelain. It can withstand far higher temps than the headers can make. The crack plug was from the header install. If you didn't remove the plugs to install the headers, it would be amazing that only one cracked. If you did remove them, you possibly put them back in too tight and cracked one of them. Or you didn't use the proper rubber lined socket when R&R the plugs and it cracked one.
Thread Starter
Burning Brakes
Joined: Oct 2017
Posts: 1,230
Likes: 467
From: Colorado
It is certainly possible I "touched" a spark plug or two during header fitting - realizing the spark plugs needed to be removed. So, I did (after manifold -- uhhhg -- removal). Spark plugs didn't get near the headers. Torque to spec (forgot spec - 14mm plugs though). The headers had been on for 8 months now. I guess I should go ahead and heat wrap the headers to mitigate potential future shitty GM spark plug issues. If it persists, I'll replace to the NGK Iridiums and new wires.
TY'all!
TY'all!
Le Mans Master
Joined: Aug 2007
Posts: 6,473
Likes: 297
From: Orange Park FL
Heat won't crack porcelain. It can withstand far higher temps than the headers can make. The crack plug was from the header install. If you didn't remove the plugs to install the headers, it would be amazing that only one cracked. If you did remove them, you possibly put them back in too tight and cracked one of them. Or you didn't use the proper rubber lined socket when R&R the plugs and it cracked one.
Pitt
Last edited by pit-man; May 12, 2021 at 02:13 PM. Reason: spelling
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