White ground strap on spark plugs. Its a puzzler!

**atlantadan** · 01-13-2017, 10:28 AM

Context: ERE 383 w/TrickFlow heads with about 7k on it. Pistons are hella noisy due to piston alloy, short skirts, and some other stuff. Karl is building me another shortblock with tighter clearances and different alloy pistons. Slap decreases a lot once warm, but still always there somewhat. LT4 knock module. 2.93 gear. 3k Yank stall. CIA headers and CIA high-flow cats - cats have at least 5-7 years on them. Car spends 99% of its life in light-to-light, sub 45 mph city driving (Atlanta. Yay). Car doesn't eat coolant at all (this will be important later...). 12-13 MPG in town with a lot of sitting in traffic. Honestly don't know the hwy MPG's since I'm never on it.

I've been chasing down some knock-counts (with the assistance of Moe Bailey) with this car and in the process have started adjusting my plugs heat-range. Karl thinks the knock-counts are due to the pistons, but there were times in the summer where I thought i could hear some detonation, so I started to look elsewhere. I was originally running the OEM heat-range on 11.4 CR, gapped to .040. Car ran great, but the knock counts were still there in the logs and my NOx was a touch high due to high combustion temps. Not enough to bomb the smog test, but really really close. When I pulled the plugs, they'd been running for 7 months and all looked pretty good. No soot, porcelain a nice grayish/brown color. No soot on base-ring of plug, nor on the ground strap. No signs of detonation - plugs looked clean and completely serviceable, but in the interest of testing, I called NGK and told them all my mods. They suggested dropping down two heat ranges, so I did.

Gapped to .035. The car started to miss on hot-restart within about a week. Pulled the plugs and the ground straps were white, with black electrodes, and wet looking black all around the base-ring of the plug. Porcelain was stark white. Some Google-fu'ing yielded very few results of white ground straps, but among them was talk of white being coolant deposits. So, repeating above - the car does not eat coolant at all, so there's that. Others said that a white ground strap means its running way, way too lean, but the logs don't show this to be the case.

I increased the heat-range by one (so one colder than stock) Gapped to .035., and motored on down the road. Within about 2 weeks, the car started to miss on hot restart. Got to the point where it flat-out would not clear up after driving. Pulled them out last night and more of the same - wet-looking black around the base threads and base ring of the plugs, white ground straps and porcelain.

As of last night, I popped the original heat-range Autolites in there, gapped to .040.

Anyway, I guess the question in this wall-of-text is regarding the white ground straps and fouling. Both sets of plugs had run about 1-2 weeks, so they only had about 150-300 miles before they started to give me issues with fouling. Does the car just want the OEM plugs due to doing lots of around-town motoring? Whats with the white?

Thanks in advance

***SSlowBoat*** · 01-13-2017, 11:17 AM

Originally Posted by atlantadan

Context: ERE 383 w/TrickFlow heads with about 7k on it. Pistons are hella noisy due to piston alloy, short skirts, and some other stuff. Karl is building me another shortblock with tighter clearances and different alloy pistons. Slap decreases a lot once warm, but still always there somewhat. LT4 knock module. 2.93 gear. 3k Yank stall. CIA headers and CIA high-flow cats - cats have at least 5-7 years on them. Car spends 99% of its life in light-to-light, sub 45 mph city driving (Atlanta. Yay). Car doesn't eat coolant at all (this will be important later...). 12-13 MPG in town with a lot of sitting in traffic. Honestly don't know the hwy MPG's since I'm never on it.

I've been chasing down some knock-counts (with the assistance of Moe Bailey) with this car and in the process have started adjusting my plugs heat-range. Karl thinks the knock-counts are due to the pistons, but there were times in the summer where I thought i could hear some detonation, so I started to look elsewhere. I was originally running the OEM heat-range on 11.4 CR, gapped to .040. Car ran great, but the knock counts were still there in the logs and my NOx was a touch high due to high combustion temps. Not enough to bomb the smog test, but really really close. When I pulled the plugs, they'd been running for 7 months and all looked pretty good. No soot, porcelain a nice grayish/brown color. No soot on base-ring of plug, nor on the ground strap. No signs of detonation - plugs looked clean and completely serviceable, but in the interest of testing, I called NGK and told them all my mods. They suggested dropping down two heat ranges, so I did.

Gapped to .035. The car started to miss on hot-restart within about a week. Pulled the plugs and the ground straps were white, with black electrodes, and wet looking black all around the base-ring of the plug. Porcelain was stark white. Some Google-fu'ing yielded very few results of white ground straps, but among them was talk of white being coolant deposits. So, repeating above - the car does not eat coolant at all, so there's that. Others said that a white ground strap means its running way, way too lean, but the logs don't show this to be the case.

I increased the heat-range by one (so one colder than stock) Gapped to .035., and motored on down the road. Within about 2 weeks, the car started to miss on hot restart. Got to the point where it flat-out would not clear up after driving. Pulled them out last night and more of the same - wet-looking black around the base threads and base ring of the plugs, white ground straps and porcelain.

As of last night, I popped the original heat-range Autolites in there, gapped to .040.

Anyway, I guess the question in this wall-of-text is regarding the white ground straps and fouling. Both sets of plugs had run about 1-2 weeks, so they only had about 150-300 miles before they started to give me issues with fouling. Does the car just want the OEM plugs due to doing lots of around-town motoring? Whats with the white?

Thanks in advance

Probably just wants oem plugs. Is your ignition system getting weak or the injectors dumping too much?

Sent from my SAMSUNG-SM-G935A using Tapatalk

**atlantadan** · 01-14-2017, 03:33 PM

Originally Posted by Tubby Z28

Probably just wants oem plugs. Is your ignition system getting weak or the injectors dumping too much?

Sent from my SAMSUNG-SM-G935A using Tapatalk

Everything is new ACDelco stuff going through Taylor 8.5mm wires. As far as I can tell, its all in great shape. Logs show the car to be running ok, if anything - its a bit on the lean side at WOT, but I'm rarely at WOT, so there's that.

Here's some pictures of the plugs.

Left - BKR7E (2 colder), 300 miles. Center - BKR6E (1 colder), 200 miles. Right: Autolite 1601 (stock), 7,000 miles
IMG_20170114_120413.jpg

IMG_20170114_120506.jpg