Out on my car tonight, I noticed sparks from the number 3 and 7 plugs. Originally, all of our cars were equipped with metallic heat shields to cover the boots. The sparks were jumping from the metallic shields onto the block.

Does that mean that the wire is bad?

Does that mean that the porcelin on the plug is cracked?

Does that mean the heat shields need to be filed down so they don't touch the block to complete the circuit?

Does anyone still use the metallic heat shields on the plug boots?

 

If you see a spark actually arc to ground, then the wire is leaking voltage. Most of the time it is not a plug problem and they don't usually just crack by themselves after being installed a while. The shields should not cause you a problem on good wires. I still have all the factory shielding on mine.

 

Thanks, that was my concern. If the wire was in good shape, the metallic heat shield shouldn't make a difference.

I'll replace the wires this weekend... ARGH!!!

About the plugs, I replaced them about two weeks ago. I put a rag underneath to catch them if they fall. Some did... I inspected the porcelin and the gap each time and they looked fine. How can I tell if the porcelin is cracked (microscopically). Thought - If I rub grease on the porcelin, wouldn't the grease go into the crack and identify it with a line? They looked great so I put them in. Bosch +4 at $6 each isn't going to be fun.. not to mention with the Edelbrock Headers it will take hours.

 

has anyone shaved the tabs off the metallic heat shields so that they don't touch the block?