[C5Natie]

With the other plugs i saw 28.7-29* max. With the cold plugs, 31.9*, so you may be right. Hey as long as it aint knocking.

[Damian]

The ECU sees things are running better and it's just running the way it's supposed to now. The NGKs really made the GTO run much smoother when I put them in.

[C5Natie]

I took a look at the NGK's today after a few weeks of driving.

Didnt like the little black speckles on the porcelain. Im thinking I should pull another 2-3* of timing.


Cylinder #7, the problem cyl in LS motors. Light tan color on one side of the porcelain. ?

[94cobra69ss396]

Those plugs look great.

[C5Natie]

Yeah Im always paranoid but it seems the ngk tr6 were the right ones. The car runs better. Im going to Willow Springs tomorrow and I just wanted to be on the safe side. I might just bring the timing down to 26* vs 28*. Ill check the data at the track.

[C5Natie]

Copy and pasted from my thread on CorvetteForum...

Thanks to working nights and nasty Folgers coffee, I researched and solved my spark plug dilema...I hope. Lol. For those who may find this useful....If you read this thread I changed my Autolite 103's because they looked fouled. Turned out it wasn't because they were too cold, it was because of octane booster that was in the gas tank when i installed the new motor. Anyway. I changed to NGK tr6's but started seeing slight hints of detonation, very light black specs on the porcelain, nothing crazy but they shouldnt be there and the first thread or two looked like they were getting hot, even though I always had good air fuel ratio readings (12.8-12.9 wot). So before I messed with the tune or went to a colder plug I looked into it. The tr6 plugs has an entire thread exposed into the combustion chamber, they're a thread longer then the 103's. This reduces its ability to dissipate heat into the cylinder head allowing the plug to get too hot. The Autolite 103 does not expose any threads and it is actually closer to a NGK heat range 7 (br7ef), then a tr6 in the 6 heat range, which is one lower then stock. Its design is slightly colder. In fact, the Autolite 103 appears on the cross reference for both NGK tr6 and BR7EF. Autolite usually has two plugs per other manufacturers heat range. No wonder the car ran good from the get go with them even when they looked fouled and especially since the car was tuned with them (obviously allowing for a bit more timing). So, in short, follow your gut because now I'm going back to the 103's. Posted this in case you're ever trying to decide on one of those plugs.

I should have some old Autolite 103's at home. I will try to get pictures comparing the threads to the NGK tr6.

[94cobra69ss396]

I can't see any spots in the pictures you posted but that just may be my computer. How did yours look after running it at the track?

[C5Natie]

Originally Posted by 94cobra69ss396

I can't see any spots in the pictures you posted but that just may be my computer. How did yours look after running it at the track?

Baeically the same. Some light speckling. Its probably from some light detonation of fuel even tho I didnt read knock. I was still seeing 31* of timing on the straights wot. I would really be worried if the speckles were silver but theyre not but still it looks like theyre a bit hot. Also I need to swap over to the newer pcv system. I think my current setup is allowing too much oil vapor to get in the intake, which these cars are infamous for. Its not much but I like my intake dry. The plugs arent fouled or anything but Im not sure if any of the speckles can be attributed to a bit of oil.

[C5Natie]

Originally Posted by 94cobra69ss396

I can't see any spots in the pictures you posted but that just may be my computer. How did yours look after running it at the track?

[C5Natie]

NGK (nickel) vs Autolite 103 (dark) thread depth. NGK is half a thread longer. Tried to compare as best as possible from where the tapered seat begins, which is where it meets the head. NGK is longer. I know the Autolites sit flush in the combustion chamber, I checked it when I got the heads new. So that means the ngk must protrude which doesnt help it dissipate heat.





Camera angle might throw off the line but theyre as close as my eyes allow.