• The site migration is complete! Hopefully everything transferred properly from the multiple decades old software we were using before. If you notice any issues please let me know, thanks! Also, I'm still working on things like chatbox, etc so hopefully those will be working in the next week or two.

Plug Gap and Rotten Eggs



Its not misfiring.
Not sure I can just do that in this case. I have unknown variables here that I have to consider as well.

The plugs installed are NGK R TR55 V-power.

First question: After 100k miles +/- 5k or so. How much do you suppose the gap would open up during that time?
 
rotten egg smell? bad cat for sure.
never heard or known of misgapped plugs doing this. even after 100K, the plug wouldn't erode that much
 
Maybe a coincidence then.

The plugs have been replaced, with new NGKs.

When I pulled the old plugs, I checked them and they all ranged from .073-.078 and had been burning clean.

I have no spec sheet to know for sure.
10 years ago when the original plugs were installed, it was commented "thats a big gap, going to run cold" about the plugs. I do not remember what it was then.

Not knowing what the original setting actually was, I split the difference and set them to .075. I did this because if they were set to .60, I did not see the plugs opening up from .060 to .078, that seemed entirely too much.

So here is where my thoughts were going. With such a big gap, currently at .075 could it be that the plug is not burning all the fuel that it is receiving due to being such a cold spark. I am also thinking that maybe setting the gap to .070 may help?

I did not notice the smell until after replacing the plugs.
 
Last edited:
Doubt that the gap is doing anything but it's not a good idea to run a .070 or higher gap.

The more power you make, the smaller the gap needs to be. Copper plugs will eat away fast for sure in a 3800 because of the waste spark ignition system. Set them to .050 to .055 gap and leave them, they are already a colder plug than factory.
 


I understand what you are saying.

But are there any scenarios you can think of that would call for a setting such as that?

These mods were all shipped together and ready to bolt on. Gaskets, intake, K&N filter, plugs, thermostat, pcm, cat back exhaust, pulley, belt, wires etc. Just plug and play. It was when all the components were being laid out when it was noticed that the plugs had a gap larger than .060.

I am not necessarily opposed to setting them to .050-.060, but if at all possible I would like to put the way it was first.

Just trying to rule out the plugs causing the rotten egg smell. Just entertaining the coincidence is all.
 
Last edited:
lol, did you fall for a "stage kit"?

Please say, no.

Regardless, the catback is the least of any flowing issues.

Send it back and get a Downpipe (with a u-bend delete...because that is the REAL issue).

As for the plugs...run better plugs. Autolite cheapo copper core 104's. Gap them at ..050". It works. 100/100 times.
 
So you want to improperly gap your new plugs, because the old ones you took out were improperly gapped? If your spare tire had 0 psi in it when you first checked it, would you keep it at that pressure, or put it where it's supposed to be?
 
99GT2dr said:
So you want to improperly gap your new plugs, because the old ones you took out were improperly gapped? If your spare tire had 0 psi in it when you first checked it, would you keep it at that pressure, or put it where it's supposed to be?
Click to expand...

Not at all, but in my defense I asked this question earlier and no one answered it....
But are there any scenarios you can think of that would call for a setting such as that?

Are people still going to tell me it is 100% totally wrong to use a smaller pulley and not put on headers? Its those type of misconception that I am trying to weed out. I am no expert but I know that is also 100% false.

I also asked earlier, First question: After 100k miles +/- 5k or so. How much do you suppose the gap would open up during that time?
Again no one answered the question but had no problems telling me I am wrong. If I am wrong, why?
 
blueguy said:
lol, did you fall for a "stage kit"?

Please say, no.

Regardless, the catback is the least of any flowing issues.

Send it back and get a Downpipe (with a u-bend delete...because that is the REAL issue).

As for the plugs...run better plugs. Autolite cheapo copper core 104's. Gap them at ..050". It works. 100/100 times.
Click to expand...

I did not fall for anything.
 


To answer your first question it totally depending on plug type/brand. A copper plug will be litterely nothing after 60-70k miles, seen it many times of chrysler motor from jeeps/dodge's. Like almost double the factory spec.

Iridium tipped plugs are made to last 100k in most vehicle, the gap from what I've seen might have moved 5%?? Done alot of plug changes on Vortec LS truck motors and they are fine gap wise but old plug wise and need of changing.

Not saying they couldnt open up more but it's not super common and nobody is going to have hard data to back anything up here.


And dropping pulleys without anything else is still a bad idea, unless you are running some 100-116 octane fuel all the time. And your first first question, incorrect plug gap won't cause a rotten egg smell. If the vehicle does not have a misfire, no real unburned fuel left to smell because the cat converter is there to burn up the rest.
 
rkm said:
Not at all, but in my defense I asked this question earlier and no one answered it....
But are there any scenarios you can think of that would call for a setting such as that?

Are people still going to tell me it is 100% totally wrong to use a smaller pulley and not put on headers? Its those type of misconception that I am trying to weed out. I am no expert but I know that is also 100% false.

I also asked earlier, First question: After 100k miles +/- 5k or so. How much do you suppose the gap would open up during that time?
Again no one answered the question but had no problems telling me I am wrong. If I am wrong, why?
Click to expand...

Well, first post in this thread by FFDP: "Run a .050 to .060 gap." So, answered 3 days ago. Then mguzzo answered your question about the gap "opening up": "even after 100K, the plug wouldn't erode that much." That one answered as well.

If I was a betting man, I'd say the PO didn't gap the plugs at all, he just took them out of the box, assumed they were pre-gapped, and .070 is just what they were at when they left the factory. Don't be the PO, gap them correctly (spec is .060, most of us tighten it to .055 because we have mods, some to .050, some even smaller for nitrous setups). Ideally, you want to run the widest gap possible (up to spec of .060, not .070+) without spark blowout. If you're so inclined, you can play with the gaps and see what your car likes and how wide you can go.

Not sure who told you headers were a REQUIREMENT for a smaller pulley, but that's no reason to just assume a .070 gap is ok when spec calls for .060. You're wrong because the damn spec calls for .060, google it if you want. I thought the gap specs were pretty much common knowledge.
 
Fivefingerdeathpunch said:
To answer your first question it totally depending on plug type/brand. A copper plug will be litterely nothing after 60-70k miles, seen it many times of chrysler motor from jeeps/dodge's. Like almost double the factory spec.

Iridium tipped plugs are made to last 100k in most vehicle, the gap from what I've seen might have moved 5%?? Done alot of plug changes on Vortec LS truck motors and they are fine gap wise but old plug wise and need of changing.

Not saying they couldnt open up more but it's not super common and nobody is going to have hard data to back anything up here.


And dropping pulleys without anything else is still a bad idea, unless you are running some 100-116 octane fuel all the time. And your first first question, incorrect plug gap won't cause a rotten egg smell. If the vehicle does not have a misfire, no real unburned fuel left to smell because the cat converter is there to burn up the rest.
Click to expand...

Now thats the info I am looking for.

So, I will assume when the plugs were originally installed roughly 100k miles ago, and IF the plugs started at .060, it would be safe to say that after that time the gaps could be .078 when removed. They are now set to .060. Admittedly, I have not used copper plugs that much.

Which leads me to ask.....If I am getting the rotten egg smell, does that mean the cat is bad, going bad, or something else? No codes as of yet.
 
99GT2dr said:
Not sure who told you headers were a REQUIREMENT for a smaller pulley, but that's no reason to just assume a .070 gap is ok when spec calls for .060. You're wrong because the damn spec calls for .060, google it if you want. I thought the gap specs were pretty much common knowledge.
Click to expand...

I was just confirming. I was unsure if the mods would change the gap specs. It is frustrating because I do not have the paperwork for the mods and the specifics of it. The specs also call for a certain serpentine belt, but I know I cant just go to Autozone and say give me a SC belt for a 01 GTP and expect them to give me the right one. Its reasons such as that why I was questioning the gap.
 
rkm said:
I was just confirming. I was unsure if the mods would change the gap specs. It is frustrating because I do not have the paperwork for the mods and the specifics of it. The specs also call for a certain serpentine belt, but I know I cant just go to Autozone and say give me a SC belt for a 01 GTP and expect them to give me the right one. Its reasons such as that why I was questioning the gap.
Click to expand...

Google-fu, it's worth training, lol. I'll tell you this, autolite 104's @ .055 will cover a wide range of setups, cheap and effective. Rotten egg smell is almost always a bad cat, if you don't have visual inspection just get a 3" catless downpipe and never worry about it again (will also need the rear 02 code turned off in the pcm).
 


Those are the types of mods I am not willing to make. I will replace the cat if need be.
 
Last edited:
You must log in or register to reply here.
Back
Top