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spark plug gap and torque needed

wgregt

NAXJA Forum User
Location
SoCal
Doing cap/rotor/plugs/wires on the '88 XJ tomorrow. Been all thru the OEM SM and the search function on this forum. That SM is damn useless for simple stuff like this. 1200+ pages and cannot find:

- the correct gap for the plugs
-the torque value (foot pounds, please) for the plugs. If I use anti-seize (Champion copper plugs) does that torque value change at all?

Thanks.
 
Last edited:
gap is .035, not sure on touque, never tourqued a set a plugs, or used antizieze on em
 
http://www.jeepforum.com/forum/f9/spark-plug-oil-drain-plug-torque-specs-846751/

from the 04 FSM for the 4.0L engine

oil drain plug 25 FT/LBS

coil rail 250 IN/LBS (21 FT/LBS)

sparkplug 27 FT/LBS

The jeep head is cast iron, and the spark plugs are steel, so over torquing on the 4.0 is not a big concern, unless you let a gorilla loose on it.

.035 gap sounds right. The parts stores like Azone should list it too if you select the jeep, year, model, engine spark plugs, I think it then displays the proper gap on the plug selections available.

http://www.cherokeeforum.com/f2/quick-easy-spark-plug-torque-question-87332/
 
Doing cap/rotor/plugs/wires on the '88 XJ tomorrow. Been all thru the OEM SM and the search function on this forum. That SM is damn useless for simple stuff like this. 1200+ pages and cannot find:

- the correct gap for the plugs
-the torque value (foot pounds, please) for the plugs. If I use anti-seize (Champion copper plugs) does that torque value change at all?

Thanks.

I'm also fairly sure it will be 0.035" - but I always check. The VECI (Vehicle Emissions Control Information) label under the hood should have the value for plug gap listed on it, use that.

Torque? I'm sure there's a given value, but I don't use it. Lightly coat the threads with never-seez, tighten the plugs finger-tight, then put a socket wrench on the plug and turn it an additional 1/3- to 1/2-turn. That's always worked for me (it's enough to keep the plug in place, but not so much that you pull the threads out of the head. The head is iron, the plug shell is steel - the iron will usually fail first, and repairing can be a pain...)
 
http://www.jeepforum.com/forum/f9/spark-plug-oil-drain-plug-torque-specs-846751/



The jeep head is cast iron, and the spark plugs are steel, so over torquing on the 4.0 is not a big concern, unless you let a gorilla loose on it.

.035 gap sounds right. The parts stores like Azone should list it too if you select the jeep, year, model, engine spark plugs, I think it then displays the proper gap on the plug selections available.

http://www.cherokeeforum.com/f2/quick-easy-spark-plug-torque-question-87332/

Are you sure it's foot lbs and not inch lbs? I know the valve cover is in inch lbs. I don't remember but 25 ft lbs seems like a lot.
 
Are you sure it's foot lbs and not inch lbs? I know the valve cover is in inch lbs. I don't remember but 25 ft lbs seems like a lot.

Yes it is ft lbs, not inch pounds. Head bolts are around 120 ft lbs. The valve cover bolts are small, easy to strip, and there is no pressure on the valve cover. The spark plugs see huge internal pressures during combustion. You want them to seal, and stay sealed.
 
Yes, anti seize affects the torque value

Isn't a 10-15% reduction of torque in order when a 'lubricant' is used? I've never checked the torque on a spark plug in an iron head, But on my Outback, with the aluminum head, it calls for only 15.2 lb. ft. I've never used any anti-seize on a spark plug, and have never had a problem. But, they will be replaced every 30k miles, and are usually pulled about half way through, to clean or re-gap as needed, so I've never had a problem with a plug being seized or galled.
 
Isn't a 10-15% reduction of torque in order when a 'lubricant' is used? I've never checked the torque on a spark plug in an iron head, But on my Outback, with the aluminum head, it calls for only 15.2 lb. ft. I've never used any anti-seize on a spark plug, and have never had a problem. But, they will be replaced every 30k miles, and are usually pulled about half way through, to clean or re-gap as needed, so I've never had a problem with a plug being seized or galled.

Yes, a lubricant does affect "applied torque" values (but not "torque angle" values - a half-turn is a half-turn, irrespective of friction.)

That's why I give the "torque angle" that I use - it hasn't failed me yet. And, you don't need a torque wrench to figure it out.

For how much to reduce applied torque according to which lubricant is used, search up my notes on the subject (here and on several other boards,) these values were confirmed experimentally, and I've been using them for years. I just don't feel like typing them out again...
 
I've never torqued spark plugs either, I set em to gudentight, basically just finger tighten then put about 1/2 a turn maybe 3/4 of a turn on them after that.

Never had any issues. Make sure to blast all the crap out from around the old plugs with an air gun before removing them, unless you like dumping road grit and grime into your engine by accident.
 
why lap your valves by hand when you can just pour sand into the cylinders and let the engine do it for you?
 
The torque value is 27 ft. lbs. Dry threads.

Go to the NTK spark plugs and Champion spark plugs web sites and look for their techincal sections. They have some good info on spark plug installation, torque, etc. NTK site is a good guide.

I don't use anti-seize because I use the NTK plugs. I torque to FSM 27 ft. lbs. Never had a problem removing my plugs.

'99 4.0
 
I've always done it finger tight then another half-turn, but the shop I use sometimes showed me the crush washers on the spark plugs weren't getting fully compressed. Now I go all the way to tight, but don't put the full monkey on it.
 
that's fine for us "blue collar" types...... Bimmerjeep might need an additional friend to pull on the ratchet, though.

I am pretty sure it requires special tools and years of experience. Probably a five thousand dollar service where he is from, after all the world revolves around NYC...
 
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