[ziddey]

I've done some searching and see most people try to dabble in iridiums or other "upgrade" plugs. I've personally always stuck with plain old coppers; they've always worked best. It also helps I've got a simple 8v i4, so spark plugs are a quick 5 minute job.

For the 80's vw's, gap spec is 0.028 +/- 0.004. California spec is 0.028 + 0.004.

For pretty much as long as I've been changing out plugs, I've gone with bosch coppers, and kept the 0.032 gap, since in theory, that should be best?

But on a current car that I've been tuning up (1990 vw fox, ke-jetronic), I've killed off all vacuum leaks; pulling almost 20 inches at idle. Full ignition tuneup. MSD Blaster 2.

Before the tuneup, car had some old bosch platinums. I'm not sure of the gap. Don't have a tool at the moment.

But after swapping in the coppers, the idle is noticeably lumpier. Still trying to fix a lean running problem as well, so I'm not putting it specifically on the spark plugs (failed smog two times in a row now. insane NOx, but that's another story, not related to this topic..)


So taking this application as an example, has anyone tried say 0.024, 0.028, 0.032, 0.035, 0.040, 0.044?

I had a 1991 vw fox; pretty much the same car, albeit with digifant management. I've also used bosch coppers on that one, and after 20k miles or so, when I goto change the plugs, I'll often find the plugs have worn down / been blown out to 0.035-0.044 easily.

What's the response to different gapping? I haven't checked to see what color spark I get, but I can't imagine it being anything short of blue, since coil, wires, cap, rotor, and plugs are all new, and I added an additional ground strap to the valve cover.