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AC Delco Spark Plugs - Install Instructions?

36K views 25 replies 13 participants last post by  sheila  
#1 ·
Hi All,

I've searched and searched but haven't found concrete info.

2012 Impala LTZ - 3.6L.

Changing the plugs this weekend with OEM: AC Delco: 41-109.

I'll be able to torque the front plugs, but not the rear due to the intake.


1st question: Gap
- Manual says .043". I'm reading some people on the forums saying .040". Thoughts?

2nd question: Torque
Online I am reading Torque spec: 15 ft/lbs. Correct?
I can torque the front 3, but not the rear due to the intake.
Is everyone just doing the 1/8th turn?

Thanks!
 
#15 ·
Yep, this was the thread that got me started here. Came in to thank that user.

I used autolite plugs for mine, gap was called for being .040 and went to tight to feel rather than attempting to use torque wrench. Dialectric for boot, but did not use any antiseize on the threads.
 
#4 ·
@jtrosky - Thanks for the reply! I've actually been through that thread and all over youtube haha.

I was planning on leaving the intake on - more curious what people have been doing to torque down the rear spark plugs?
I figure I could do the front three, gauge the angle on those, and try my best to do the same on the rear? Or has someone successfully gotten a torque wrench back there??

Second question - The manual says .043" gap - but even in that thread you shared people are saying .040. which is it?
 
#5 ·
Not sure about the gap - I'll try and check my service manual and see what that says.

To torque the rear spark plugs, I'm assuming you can do it with a torque wrench using some extensions (maybe the kind that "pivot")? I haven't done it yet myself.. I'm sure someone that has done them will chime in shortly though.
 
#17 ·
For those, like myself, who like a little more detail, here's an 8-minute in-depth video ...

Cheers!

T-

 
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#19 ·
^+1 on the great video! Only things I'd add: Dab of never-seize on the plug threads, dielectric grease applied inside the boots with a small screwdriver or cotton swab and instead of dropping the new gapped plugs down in the plug hole, I insert them into a scrap piece of 3/8" hose and gently position and start them by hand with the hose attached. When plug is started, hose will stop or slip. Pull hose off and tighten with ratchet, extension and plug socket.
 
#22 ·
I'm with you there, Sheila. A little dielectric grease, inside the boots not only improves performance, but also helps prevent the boots from sticking to the plugs next time they need changing. And I consider a bit of anti-seize an absolute must when threading steel into aluminum. Great for brass-to-steel fittings too, so I use it on my outside hose bibs to prevent the brass hose connectors from seizing to the bibs.

However, there's one thing about using anti-seize that everyone should be aware. Torque specs are almost invariably listed as "dry" numbers, and an adjustment is required for fasteners that are tightened "wet." I've seen 50% offered as the general rule of thumb for the torque reduction, but that seems excessive to me. I usually reduce the torque by 30%, and have never had an issue.



... Engine must be cold.
Another great point, Fred!

Always let those aluminum heads cool down a little before pulling the old plugs. Aluminum has a higher coefficient of expansion than steel, so you risk buggering up the threads if you remove the plugs while the head is still really hot.

Cheers!

T-
 
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#23 ·
My Impala idles like crap evry since I changed the rear 3 plugs a few months ago. I didnt remove the manifold, so Im wondering if there is now a small hose in one of the rubber hoses back by the plugs, but everything looks and feels fine.

I Bought a new plug and put it in the outer cylinder closes to the brake booster and no change, moved that plug to the middle and no change and swapped the #1 plug with the middle plug and no change. Only thing I didnt do was use dielectric grease when changing, but I have reseated the coil packs back there too, so im at a loss now of whats causing this, as my scan tool is not sowing any misfires, so im guessing O2 or a PITA vacuum leak somewhere.
 
#24 ·
You're sure you installed the right plugs? If so, you could have knocked a vacuum hose loose, which is allowing unmetered air into the system. You may be able to track it down fairly quickly by spraying some carb cleaner around back there and listening for the idle speed to increase.

Cheers!

T-
 
#25 ·
Tackled the plugs yesterday. Wish I would have taken pics of them to share! Not too rough of shape after 100k miles.

I was a little concerned with oil in one of the plug wells.. read a TSB about porous heads causing oil to leak in the spark plug well. Hoping this isn't the case here. It's not throwing any codes so I'll keep driving!

Also surprised that the factory plugs weren't gapped to spec. Measured them all at .038" where as the manual states .043". I cautiously gaped mine to .043".

I was able to sneak in a torque wrench on the rear plugs, using a 6" and a 3?" Extension. Got all 6 torqued without removing the intake manifold.

Running great after the change.
Thanks again crew!