Going to install first set of replacement spark plugs (NKG TR55's) in my '99 coupe (stock engine/stock tune) and the manual says .060 gap. Are there any other recommendations from other vette owners as to a better way to go and if so - why the change?
Thanks for any recommendations & explanations,

 

I think I read where there was a TSB stating that maybe they shouldn't be gapped that wide after all. I gapped my TR55s at .045 based on what I've read in other places. In general, a wider gap gives a better burn at lower RPM's (around town) which may affect fuel economy and such but a wider gap is harder to "bridge" at higher RPM's (where my car lives).

That's on a stock motor. When I ran nitrous on my T/A, the narrower gap was a necessity due to the higher cylinder pressures. Think of it like trying to light a lighter out in the wind. The same goes for supercharged and turbo cars.

 

I've played around with gaps on my Corvette and with my LS1 powered 98 Formula and found that .050 works best. The stock gap is too high and you're more prone to misfires and the throttle response is not as crisp. I run NGK TR55s and change them every 6 months.

 

Not to steal away the thread, but mine's a 99 coupe also. A4, 2.73 rear end. All stock car, with stock plugs (whatever they came with from factory). WILL changing to NGK TR55 be beneficial in anyway ? Car has only 23K miles on it.

Thanks in advance...

 

Thanks for the replies, its the kind of information i was looking for. When I pull the stock plugs I'll check how wide it is at that time and maybe alter my thinking. I'm now inclined to start with a gap of around .050 and see if I want to go wider or narrower from there.
Thanks,

 

Wider is better for sure to the point of misfires. Misfires are a result
of not enough voltage to fire the gap. Larger gap is bigger flame kernal
and better combustion. Thats the reason plugs have evolved from .025-
to todays standard of .060. And part of the reason for dual plugs in Pro stock drag racingThats why I change my wire's and use Jacob's The jacob's can the handle huge voltage of the hottest coils (1300+
joules) I had a Jacob's ignition w/ a 65,000 volt coil that was half a toaster,
in size. Instruction's stated to increase plug .005 till misfire ocurrs
then return to previos gap. I end up at .70 thousands and had more power, better mileage and INSTANT starting. I also always index my plugs. I run Ngk Which are recommended by Jacob's (copper only plugs) .062 gap on my z-06.

 

I'm going to take issue with that.
Any factory ignition today has enough voltage to fire across a gap much larger than the typical spark plug gap.
What causes misfire, assuming correct A/F ratio, is that the electricity will take the path of least resistance, which is not always across the gap. If deposits on the insulator provide less resistance than the plug gap, the current will take that path to ground instead of jumping the gap. More voltage won't really make a difference.
My MSD will put a spark across a 1/2 inch gap with no problem. But it won't fire a sooty plug gapped at .020, especially when cylinder pressures go up.

 

This post makes no sense. Try that 1/2 inch gap Spark has to jump to ground,What deposit's. My plugs are clean!

 

Proper replacement plug for LS - 1 is AC 41 - 985 Iridiums. They are factory gapped at .040. Instructions are that you are not to change the gap. I changed my originals at 60,000 miles. I noticed no change whatsoever in performance etc. Car runs like a raped ape ! No oil or no sieze on the threads. Good Luck !

 

Dude, calm down and think about it for a moment.
Jumping the gap isn't the only way for electrical energy to get to ground.
Any plug that has been run has deposits, whether you can see them or not. Conductive, nearly invisible deposits are even worse with leaded gas.

And yes, I'm speaking from experience when I say that my MSD has no problem jumping a 1/2" gap. Actually, I've probably seen it jump more like an inch. If you're skeptical, I'd be happy to set up a little experiment in my garage, where you place your hand 1/2 inch from the end of my plug wire, and I turn the engine over.

People who run magnetos, the highest energy ignition, typically run plug gaps of about .017. They also typically run colder plugs with a shorter path across the insulator to ground, so they foul more easily, so they need to keep the gap down. Been there. Done that. Not talkin' out of my ****!

I know it's fun to post, but you've got to expect that if you don't know what you're talking about, once in a while somebody will call you on it.

What actually makes no sense is your statement,
"And part of the reason for dual plugs in Pro stock drag racing."

 

Pressure is a huge factor. Voltage that will jump a 1" gap at ambient pressure might not manage a hundred thous at 200 psi. However, as mentioned the problem usually is a lower resistance alternative path like the plug's insulator (internal or external), out through the wire, across the body of the coil, etc.

 

You change plugs every 6 months....

How many miles?
Do you notice any benifits?


DH

 

I end up changing the plugs about every 8-10k and I do notice that the idle smooths out very slightly with fresh plugs. I know I could probably get away with changing the plugs only once a year and still wouldn't lose any major performance, but it only takes me 45min to change the plugs, and I figure it's much easier to remove them if I don't leave them in there for too long.

 

I do much the same as Patman gap at .50 ,change at 10-15k .The tr55's are $1.69 a plug so why not, plus I like to see whats going on with my plugs with the junk gas we have

 

I gap my NGK TR6 plugs at 32 - 35 because they are a colder plug and I run a Vortech Supercharger. Boost loves a closer gap !

 

This thread just keeps getting better - more or different opinions anyone?

 

Mine's a '99 also. Stock. After reading all of these posts, I'm totally confused. Anyone have any concrete info. on a plug gap that won't be detrimental to the engine or it's performance? I'm thinking I'll just go with the owner's manual.....060"

 

I'm still wondering about why people are changing their plugs so often??? Especially if using iridiums. Even regular ol AC-delco plain janes shouldn't need to be changed more than 20,000 miles or so on a stock engine -and that's if you've been hammering the pedal religiously. But, then again, plugs are cheap....and I have a little saying, "If it gives you peace of mind, why not?" But, I never have noticed any power gains or anything from changing any earlier than that. I have noticed that regular plain jane cheapy plugs will perform much better than any of that platinum or split fire type crap. The platinum plugs aren't a very conductive metal at all, and the split fires increase the surface area of where the spark jumps therefore causing the spark to be less consistent in intensity. The thing that both of these plugs (platinum and split) do is increase the life of the plug, but now we have iridiums to give you the best of both worlds. I went to NGK iridiums with the filed looking electrode...a proven method to increase performance...and a durable metal to hold up. They come pre-gapped.....put em in and forget about it. Otherwise, just use the cheap plugs....they're usually best in the performance arena. Just my thoughts. As far as gap, I usually run 0.50 also....my compression is 10.25:1 and I don't have any problems with stock plugs, or the NGKs firing at 6000 rpms (haven't seen much higher than that -so don't know about up to 7000). I just have an old HEI ECU controlled distributor too. As for idle, if your looking for perfectly smooth idle...get a cadillac...hehe...just kidding...well it should idle smooth enough. If your not getting your fuel burned with a .50 spark, then you need a multispark capacitive discharge box (MSD6AL)...with plug wires that can handle it....but mostly this only happens on extreme race motors that have to run alot of extra fuel. -Well, that's the way I understand it anyway.

 

Call me on What! Dude,
I assure you I've had more plugs in and and out than you can count.Jr.
Dad had a gas station for years for christ sakes.
and my first post is absultely correct. When we had the old points,gaps were say 28-32,Because there was not enough voltage to dependly light a larger gap.Electronic ignition replaced the points gaps widened. Wider is better, Wider gap needs more voltage Want learn something
call Jacob's and talk to there tech's take your issue's up with them.
Don't care what you think you know. They have 8 coils on a LS-1, one on a
prevoius v-8 Why! hotter spark.LESS Fouling, My 4 cly pick up has 8 plugs
Why more flame kernal, Factory found more power, better combustion.

 

Always use anti-sieze when installing plugs. I saw someone mention that they change plugs often to see what's going on in there....not a bad idea, really....I usually just go around and pull each one and check them out that way looking for tell tale signs....so if your using the cheapys...why not slap some fresh ones in? But, I definitely agree with the .50 gap...on an AC 45 or hotter plug....Also, plug gap is more dependent on the plug characteristics of that particular plug than what the service manual recommends....unless of course, it is a stock plug...then again, I usually run a little shorter gap than what the manual recommends b/c I am a pedal beater.