Which NGk and gap

[Supersport0126]

Quick question guys. I did the search on this but would rather have some quick up to date info. Kind of stupid question, but what's the best plug to run these days? I was thinking tr55 or tr55ix. It's really hard for me to decide which one of those to get. If they are still the best to use in ls1s. And also what gap should I set either one at? I'm a 98 ss full bolt ons,4k yank, not driven much at all. Really having hard time making this stupid decision. Just don't wanna put ones in or with wrong gap and have to take me back out. Thanks!

[pajeff02]

I run TR-55s in ours with the gap set around .050". Not familiar with the "ix" plug, but if that is there version of an iridium plug then gap would be around .040".

[Supersport0126]

I did end up buying the iridium plug. I bought them new off eBay and it was not sated what the gap was. Will I be ok if it's around .60? Even with my mods? Someone posted a Tsb about .04 less from .60 every 50 hp added if I read it correctly. Not sure if it applied to a 98 ls1 like mine. If their at .40 should I run .50 like yours? Should I leave them be if .40 or .60? Not touch them at all because their iridium? Not sure if I ever gapped iridiums. How sensitive are they?

[pajeff02]

If they are the correct application and heat range I would simply check to make sure they are all the same and install them.

[SteveC]

I run TR-55s in ours with the gap set around .050". Not familiar with the "ix" plug, but if that is there version of an iridium plug then gap would be around .040".

+1 on this for a N/A engine.

[Supersport0126]

Just got them and they are all at .60. Can and should I drop them to .40 or .50? Or leave them go. .60 is so big. I don't want to have to take them back out

[2002ssslp]

Never touch iridium plugs. If you have the correct plug with the correct heat range just put a little anti-seize on the threads and install them. Messing around with the gap may damage the plug.

[SteveC]

If you purchased the TR55 (copper) you CAN regap them, mine are set to .055

[theorangeguy]

pretty sure the ones you are talking about come pre gapped...you dont want to gap them because you'll mess them up.

[Supersport0126]

Are the tr55 more recommended than the ix's? And aren't these new iridium plugs supposed to be at .40? I just want these to be right for the car. I'm just trying to find this out

[pajeff02]

Iridiums are "install and forget" style spark plugs for up to 100,000 miles. The TR55's are copper plugs that may get you 30,000 to 40,000 miles. You are not going to notice any difference between the two imo.

[Supersport0126]

Guess I'll just put them in. I was just trying to get this gap situation figured out. If they would be better at .40 or .50 rather than .60? Thanks guys

[pajeff02]

From the Denso Iridium FAQS:

Q. Do I need to set the gap?

A. Generally, no. The DENSO Iridium Power plug comes pre-set with a protective sleeve over the firing end, to protect the gap from accidental alteration. DENSO Iridium Power?s ultra-efficient firing power compensates for normally recommended gap settings that are smaller than the pre-set value. In the cases of vehicle modifications (nitrous, turbo-chargers, super-chargers, high power ignition systems, etc.), some adjustments may be desired. Or, if you prefer to remain consistent with factory specifications, you may adjust. However, please be careful not to place any stress on the fine center electrode during adjustment. You could accidentally break off the very hard, and therefore brittle, tip.

[Supersport0126]

Thanks a lot for the info jeff. Appreciate it very much. I'm putting them in now. When I do them again maybe I'll get them at .40. See if I notice anything?

[pajeff02]

With it being one coil per plug... rather than the good old days of one coil per eight plugs, there is all sorts of saturation time between ignition events. You should be just fine. If the engine doesn't like it for any reason you'll most likely get a misfire code.

[Supersport0126]

With it being one coil per plug... rather than the good old days of one coil per eight plugs, there is all sorts of saturation time between ignition events. You should be just fine. If the engine doesn't like it for any reason you'll most likely get a misfire code.

Yeah I should be alright. Thank again man. Hey you happen to live around Robinson township? That's where I'm at. Or do you ever go up to the drag strip in new Alexandria?

[pajeff02]

We're up in Tioga County (about 45 miles north of Williamsport) and have a place in Snyder County 2 miles south of Beaver Springs Dragway.

[Naaman]

I recently changed my plugs; I went to the parts store looking for TR55s, but the guy handed me "TR5s" (iridiums) instead. I looked them up and they were the correct application. After the install, I noticed significantly improved fuel economy. The way I drive, I used to get about 285 miles out of a fuel tank on my Autolites. With the TR5s, I consistantly get 310-320 miles per tank and I am heavy on the pedal as often as I can get away with (haven't changed my habits one bit).

[pajeff02]

^^ How badly worn were the plugs you removed?

[Naaman]

I'm not sure, but the fuel economy they delivered was similar to the ones they replaced (which were NGK TR55s). I will acknowledge that there may have been a problem with the Autolites because the number 8 plug came loose at one point. It was tightened back up, and then came loose again.

I also noted some oil on the threads of at least one plug (IIRC). Had the shop install the new ones and give me back the old ones. So, I'm not sure which cylinder that plug came out of.