I recently developed what I suspect is an exhaust leak from my Kooks manifold gaskets. So while I'm waiting for the new GM gaskets to arrive, I was thinking about maybe changing the plugs out while I'm in there for no other reason than me having to remove the wires and get dirty anyway. Plus they are the original plugs from my build 6+ years ago? Granted they only have about 40k miles on them. Anyway, I removed plugs 3 and 6, just because they were the easiest to get at and I wanted to check both sides. The plugs look good except they're gapped at .065 and .068. They're NGK TR55s which I believe come pregapped at .060. I just don't know if these were intentionally gapped like this or did something happen to open them up?

The car is a H/C/FAST LS2 with a slightly bumped CR. Most of my research shows I should be using TR5s gapped at .035 - .040. Although I see some people running TR55s gapped down to .040 but research also shows NGK messed up when listing the TR55s for the LS2 because dropping the gap from .060 to .040 isn't a good idea.

So after all of my rambling, do you think my plugs were intentionally gapped that big, and if so, any theories as to why? Or was there an internal problem which may have opened them up? And am I correct in now going with the TR5s at .040 for my build?

Thanks

 

You changed out your plugs 40k miles ago and going by what you said you have no idea upon installing them what the gaps were. Now after removing them you are measuring them and find a discrepancy. Well, who is to know at this point. From what I know any and all spark plugs for your car should be 0.040 from what I understand. I recommend the original plugs that came with it. If you used original GM exhaust manifold gaskets, I am surprised they are leaking. Use some blue thread lock, make sure you torque the bolts and make sure the bolts are not too long and are bottoming out before compressing the gasket. Maybe you want clean the head threads with a tap and make sure there is no build up in the bottom. I have seen guys use the original bolts and with some headers the bolts need to be 1/4 " shorter so not to bottom out before compressing the gasket .

 

The Kooks gaskets may not be metal like GM gaskets. The Gaskets that came with my ARH's were like asbestos cardboard and I didn't use them for fear of leaks so I bought a set of GMs and had no problem. As to plug gaps, I run TR6 plugs gapped at .036 per my tuner's recommendation. I can't imagine running the gaps you are talking about. If you put them in, you should remember gapping them.

 

Let me clarify. I did not install these plugs. The shop who did the build 6 years ago installed them. Since it is the weekend I cannot get a hold of them so I was looking for a more immediate answer plus a little knowledge. I too was amazed at the gap and I can't see them setting them up this way. Which is why I was asking if it's possible something opened them up? I've heard of gaps closing but not opening.

As for the gaskets, I have to assume they are the gaskets that came with the Kooks (shop installed these too) which is why I am replacing them with GM since the Kooks gaskets don't have a good rep, although they've held up this long.

SUB VETTE, what set up do you have? As of right now I plan on going with TR5s at .040.

 

Mine are NGK TR6GP's

 

Spark plugs gaps are supposed to change after 40,000 miles. The electrode and ground slowly burn away with every spark. The hotter the spark, the faster they burn. This is normal especially if running hotter ignition coils.

 

I'm sorry, I meant what type of build do you have? I'm curious if it's similar to mine.

This makes sense, thanks. But do you think it's possible it opened up from .040 to .065 or is it more likely it went from the manufacturer's gap of .060 to .065?

I'll be trying to get in touch with my tuner today but all things still show me needing TR5s .040.

 

[QUOTE=5knives;1590089868]I'm sorry, I meant what type of build do you have? I'm curious if it's similar to mine.



Just bolt-ons - Ported TB, ported Fast maniford, K&N intake, 180 thermostat, Corsa Sports exhaust, tuned.

 

Ok thanks. The TR6s are 1 heat range colder than the TR5/55s correct?

I'm still reading where some people are gapping the TR55s at .040. Isn't that too much of a drop from the pregapped .060? I read the TR5s(.040) and TR55s(.060) are the same heat range just pregapped differently. Since the TR5s are the same heat range as the TR55s wouldn't it make more sense to go with TR5s if you want a .040 gap or am I missing something?

 

I've seen plugs that looked like someone filed the electrode away. Haven't used NGK's but if they aren't platinum their gap will erode away.

 

[QUOTE=5knives;1590090316]Ok thanks. The TR6s are 1 heat range colder than the TR5/55s correct?

Yes.
Regarding gap changes, I just put a new set of TR6's in, replacing a similar set with about 30K miles on them. The gaps on the used plugs had opened up from the original gap of .036, which I had set, to .040 - .041 after that much use.

 

[QUOTE=SUB VETTE;1590092720]The plugs opening .05 makes more sense than mine opening .25 which leads me to believe they were originally gapped at .06.

I just swapped in a set of NGK TR5 Laser Iridiums that Pepboys had in stock. NGK states the TR5s are the correct plug for the LS2 pregapped at .040, which goes along with my research. The only discrepancy is whether the Copper plugs would have been a better performer than the Iridiums, which seems to be the consensus. However, I'm skeptical there will be measurable let along noticeable difference between the two.

 

there might be a change in performance, esp. if the plugs you replaced did start at .60 and you now have .40 plugs in there.

 

The most up to date information indicates my car and build should be .04 which is what the TR5s are. When my set up was built everyone, including NGK, said the TR55s were the correct plugs and a lot of owners/tuners were gapping them down to .04 from.06, which is too much in my opinion. NGK recently corrected the info to state the TR5s are the correct plug, which comes pregapped at .04. They're exactly the same plug other than gap size. I have a feeling my plugs were put in with the assumption they were pregapped correctly from NGK. Now, how this will effect my original tune I'm not sure.

My comments regarding a power/performance difference was directed towards the Copper vs Iridium.