To Gap or Not To Gap

[Pat]

that is my question. I recently purchased a set of Denso IT-20's and after reading many (if not all) posts relating to this plug I am unsure if gapping the plug is necessary, what spec's apply and even the torque value when installing.

The only things I'm sure of is that the engine must be cold, and the center electrode must not be touched by a tool.

DR Automotive recommends, I believe, that the plugs be left alone. Others specify gaps that range from .04ish to .05ish. Some use lubes, others not, some have reported catastrophic plug failure, others are having a normal plug life expentancy.

My mechanic is standing by awaiting my answer. He's dealt with Denso's on a regular basis, albeit exclusively with ricer turbo cars, and depending on boost levels found gapping the plug to be necessary to keep the plug firing.

However, my MM is NA so what should I do, gap or not gap and to what spec?
At $12.00 per plug, it's not just another part, it's an investment.

Thanks

[RF Overlord]

pat, I used the Denso's before I got blown, and, on Dennis's recommendation, I installed them right out of the box. I also didn't use any anti-seize at that time, although when I installed the new Motorcrafts with the blower I did use just a smidge...

[Smokie]

I installed right out of the box, NO gapping, no thread goo. I was n/a and my car performed very well. I noticed your sig. mentions nitrous, I do not know if Densos are recommended for nitrous applications.:)

[Pat]

I installed right out of the box, NO gapping, no thread goo. I was n/a and my car performed very well. I noticed your sig. mentions nitrous, I do not know if Densos are recommended for nitrous applications.:)
Smokie:

I did a little research on Nitrous equipped cars and the consensus seems to be
that copper core, short ground strap designs over stock plugs.

Iridium plugs in a colder range are also perferred. The big no no was platinum plugs because of heat/melting issues.

[David Morton]

They should be pre-gapped, but you should check the gap anyway just to be sure they didn't get mashed in shipping.

You need the anti-sieze because the threads in the head are aluminum and the plug is steel. Because the electrolytic action between the two metals will cause the aluminum threads to corrode you need the lead-based lubricant to keep your aluminum threads nice and corrosion-free.

[BillyGman]

that is my question. I recently purchased a set of Denso IT-20's and after reading many (if not all) posts relating to this plug I am unsure if gapping the plug is necessary, If you've read "ALL" the posts relating to this topic, then I'm afraid there's nothing more to add since there's been some spirited debates about this which have included just about every angle of this issue. So any further commentary would merely start up yet another debate on this. Been there done that.....good luck with your decision....

[GreekGod]

Like Mr. Morton said, ALWAYS use anti-sieze on plug threads. Never allow any of it on any surface of the plug exposed to the combustion chamber as it is a conductor and could cause spark problems.

[RF Overlord]

Please understand that I am not disputing David Morton OR The Humungus, but the factory doesn't use anti-seize...I've heard compelling arguments BOTH ways, and I'm still not convinced either way...

HELP, Mr. WIZARD....!

[carfixer]

I've never used anti-seize on spark plugs on aluminum heads. The factory doesn't use it either. They have a 100K mile service interval and I've replaced many plugs that have gone the distance with no issues.

[Pat]

A reading of the Denso box reveals important, I believe, info. The plugs come in two styles, a tapered fit and a crush washer flat fit. The IT-20's are tapered. Torque values are not mentioned but installation instructions are given for both styles. After seating with a suitable tool the washer style is further tightened 1/4 to 1/2 turn. For the tapered style, the plug is tightened 1/16 of a turn. That would probably convert to a torque value.

Other information such as melt down temperature ranges for different metals, performance improvements and radio frequency resistance is ohms are given.

What is noticeable by it's absence is gap values and instructions. Maybe that answers my question, don't gap.

Thanks for the input fella's.

To the track when temps get into the 70's here in the Arklatex. Soon I hope, my porch thermometer is reading 92 @ 5:30.

[GreekGod]

This is (only) one of the mysteries I've run across over the years! Many moons ago my moccasins and my mind became moored to mysterious maladies of (apparent) miscreant misconduct. I've forgotten many but one that comes to mind is the old "why don't they put zerks in the u-joints anymore?". Well, I was told (circa 1970) the manufacturers save 10 cents on each joint and get to sell more joints after the warrenty runs out. This would amount to $ 200,000 on a 100,000 car run of RWD autos with only 2 joints in the driveshaft, so it did seem plausable at the time. Similar theory with no-zerk ball-joints and tie rod ends! Later I learned the hole drilled/tapped in the joint made it significantly weaker and wasn't a good idea on high stress applications such as front axles on 4wd trucks that also don't have room for the zerk anyway. More resently the story goes: "the seals are so well made and seal so tight they contain a life-long supply of grease (and also keep out water and other contaminants better than joints with zerks) so they last longer and are stronger too". As Mr. Morton said, dis-similar metals corrode and experience has taught me plugs in an aluminum head will "weld" themselves in without anti-sieze. Even iron heads will benefit from lubed plug threads, especially tapered seat style that seem to get over-torqued by installers that don't use a torque wrench or use a 500 ft. lb. impact wrench! I may be wrong but I don't believe Ford used dielectric grease on early Dura-Spark plug wire boots. Later, they told us to grease the boots and even the rotor! I'd appreciate a Ford engineer to explain why anti-sieze isn't used from the factory on sparkplug threads any why it should (or should not) be used on replacement plugs. To me it's a no-brainer open and shut case. I've also read sparkplugs that use gaskets should get a new gasket any time they are removed and re-installed! How many peeps do you know that do that?

[David Morton]

Greek God, the straight dope on the Zerk fittings is that factory analysis of failed joints of all types having Zerk fittings showed that elemental silicone (sand) was found to predominantly be the cause of premature failure. The lube techs weren't wiping off the dirty Zerk fittings before sticking their grease-gun on and shooting all that dirt right into the joint!

Carfixer's right, and the truth about dissimilar metals and corrosion is that water has to be present between the two metals to start this process. Most of the time, a car never sits long enough to allow much moisture to get very far in and when they get yanked out you never notice the 30 or so degrees of corrosion that was on the last thread, next to the combustion chamber. But install a new set and the next 30 degrees of thread will begin to corrode.

Besides it's cheap insurance. I use it on any steel part threading into aluminum. Assembly time is cut significantly and future problems are eliminated. This is especially true of water pumps and all other exterior parts mounted to aluminum blocks, heads, transmission cases, etc.

[Marauderjack]

I use "Hi-Temp" silcone grease on all threads where no recommendation for lube is offered..........NO PROBLEMO!!! :beer:

I think the torque spec for tapered plugs is 6 ft lbs or 70 in lbs.....Though I never have used a torque wrench on them?? :confused:

Marauderjack :D

[GreekGod]

<TABLE class=tborder cellSpacing=1 cellPadding=6 width="100%" align=center border=0><TBODY><TR title="Post 299222" vAlign=top><TD class=alt1 align=middle width=125>Marauderjack</TD><TD class=alt2>I use "Hi-Temp" silcone grease on all threads where no recommendation for lube is offered..........NO PROBLEMO!!! :beer: </TD></TR></TBODY></TABLE>

Silicone is an interesting alternative but it is not a conductor of electricity, or is there a di-electric silicone grease?

[Bradley G]

Regap, they are probably close to where they are supposed to be.
It only takes a few moments.

[SergntMac]

I'm not in disagreement with any opinions on the record here, I'm just logging my own personal experience.

I used Denso IT-20 in my first MM for 20K before I sold it. I have 35K on my present MM, and I'm on my second set of Denso IT-22, for supercharged applications.

I checked the factory gap out of the box, they were uniform at .036 (on the tool I use) and I made no changes. Neither did I apply any anti-seize.

I have no problems to report, or, disappointments in performance. I routinely check the plugs for information on my tune, so, perhaps I am interrupting the erosion process.

I like it when the pros check in with global advice, but has anyone here actually experienced a stuck plug on an MM head?

Also, I have been advised that .036 is too "open" of a gap for my supercharged application. Any opinions on this?

[RF Overlord]

I have been advised that .36 is too "open" of a gap for my supercharged application. Any opinions on this?Mac, I'm assuming you meant .036"...obviously Kenny Brown or Dennis would be more qualified to answer this for your application, but the Trilogy manual recommends .032"...I can't imagine a difference of .004 would really matter...

[usafsniper]

that is my question. I recently purchased a set of Denso IT-20's and after reading many (if not all) posts relating to this plug I am unsure if gapping the plug is necessary, what spec's apply and even the torque value when installing.

The only things I'm sure of is that the engine must be cold, and the center electrode must not be touched by a tool.

DR Automotive recommends, I believe, that the plugs be left alone. Others specify gaps that range from .04ish to .05ish. Some use lubes, others not, some have reported catastrophic plug failure, others are having a normal plug life expentancy.

My mechanic is standing by awaiting my answer. He's dealt with Denso's on a regular basis, albeit exclusively with ricer turbo cars, and depending on boost levels found gapping the plug to be necessary to keep the plug firing.

However, my MM is NA so what should I do, gap or not gap and to what spec?
At $12.00 per plug, it's not just another part, it's an investment.

Thanks
http://densoiridium.com/installationguide.php

[metroplex]

The factory does not use anti-sieze on the threads. Spark plugs have been known to eject from factory-stock engines before. There is a class action lawsuit currently being organized for ejecting spark plugs.

[BillyGman]

Also, I have been advised that .36 is too "open" of a gap for my supercharged application. Any opinions on this?I have mine set at .032" since that's what Trilogy recommends for their S/Ced set-ups. And as far as I know, it wouldn't matter what type of S/Cer you have as far as sparkplug gaps go.

[SergntMac]

I have mine set at .032" since that's what Trilogy recommends for their S/Ced set-ups. And as far as I know, it wouldn't matter what type of S/Cer you have as far as sparkplug gaps go. I'm going to be going over my plugs this afternoon, I'll try the .032 gap, see if it changes anything. Thanks.

[Bradley G]

I saw .030 -.035 for S/C'ed applications I kept mine to the smaller end of this range.Must not be that critical.

[SergntMac]

This past weekend, I ran a little test during a 500 mile road trip, and pulling my spark plugs for inspection was part of that. I checked the gap again, still .036 and looking good.

While doing this, I made a few calls to folks in the racing business I trust. The recommendation was to keep the .036 gap, and the reasoning behind it is spark blow-out at high RPM, aka "blowing out the candle".

It was explained to me that wider you gap a spark plug, the better the spark intensity. However, at some point, the gap can be so wide, the spark won't make the leap to the electrode, and this varies by RPM. The wider the gap, the lower the RPM where spark blow-out will occur, and supercharged applications flush this out more than N/A. For example, gapped at .040, spark blowout may occur above 4500 RPMs. Gap at .035, it may occur at 7000 RPMs, so, if you're not going this high in RPMs, you can get maximum spark without blow-out. It takes some dyno testing to discover the ideal gap, but this is the fine tuning stuff we need to know about. BTW, every engine and tune will be differrent.

A gap of .030 to .035 is a safe zone where blow-out isn't a concern. .036 is probably my upper limit, and I've done enough dyno tuning to know I have no loss of spark at high RPM, so, I'm going to leave things be for now.

[Tallboy]

I think whatever plugs you like, you should use. I doubt any of us here will leave our plugs untouched for 100k miles, so the dissimilar metals shouldn't really concern us.

[warren]

Spoke to Denso.

For N/A MM totally stock IT16's gap to .050

For N/A MM with a tune( SCTprogram,180stat etc.), IT20's and gap to .050

For N/A MM with a tune and Nitrous 75-150hp IT20's & leave
as out of box at .044

For N/A MM with a tune and Nitrous 150-250hp IT22's and leave as out of
box at .044

For S/C MM with tune IT22's and leave as out of box at .044

They do not suggest anti-seize.

Warren

[Pat]

Thanks Warren, good info, Dennis was right.

[David Morton]

Gap. I don't know what the factory gap is supposed to be but the wider the gap the hotter the spark because it takes more voltage to bridge the gap.

1- The factory spec is designed to give the hottest spark that the coils will last with. If it's too wide, the coils can overheat trying to give 50,000 volts and you wind up frying the coils.

2- When supercharging, the denser air takes more voltage to bridge the gap than N/A. So expect a smaller gap to cause the coils to produce as much voltage (and just as hot a spark) as a wider gap does N/A.

3- Jerry Barnes has obviously flogged the Trilogy system thoroughly and if he says .036", you better go with that.

4- If you're doing anything else that doesn't have a gap that's been tested I'd say either guess and be prepared to replace coils or do a dyno session and find a gap that doesn't overheat the coils.

5- I couldn't care less what Denso says.

[BillyGman]

Gap. I don't know what the factory gap is supposed to be but the wider the gap the hotter the spark because it takes more voltage to bridge the gap. The factory spec for Marauders is .054" to .056" :)


3- Jerry Barnes has obviously flogged the Trilogy system thoroughly and if he says .036", you better go with that. Okay, but just be informed that the Trilogy manual says .032" for the gap.

4- If you're doing anything else that doesn't have a gap that's been tested I'd say either guess and be prepared to replace coils or do a dyno session and find a gap that doesn't overheat the coils.

5- I couldn't care less what Denso says. ...............