1987C4

I read another thread on spark plugs and there was a mention of the torque setting for the spark plugs. When I tuned up my 1987 Vette, I did not have the factory service manual yet and used my Haynes manual. The Haynes said the torque in aluminum heads was 12 ft lbs. and that is what I used (along with some anti-seize on the threads).

Now I check my factory manual and it says 22 ft/lbs for the plug torque. I was wondering what everyone was setting them at and if I needed to go back and retighten these things. I've driven it about 1000 miles with the lower torque setting... hope this won't hurt anything!
Any observations appreciated. Thanks!
Brad

CentralCoaster

22 ftlb sounds like it could be excessive on alum heads. I'd suggest something closer to 15. I'd hate to damage those threads.

runner140*

And make sure to use anti-seize on each plug.

rick lambert

I know guys do it-but I've never used a torque wrench on plugs-I usually snug em and give them a little more-wifey likes it too
really if you know what it's like to pick up 15 lbs-that's all you need.

blown87

But do not get it on the first three threads.

Anti-seize is just very small glass beads with some sort of carrier (grease)

If you get the glass beads where they are exposed to the combustion chamber or in the combustion chamber the will glow iridescent and cause pre ignition and or detonation, which like they say in the old Tarzan movies, "Bad JuJu country, Bawana".

Mike_88Z51

My 88 GM Factory Shop manual says 18~22 ft.lb. My Kawasaki factory shop manual says 18~22 ft.lb. for the same size/thread spark plugs in the bike's aluminum head. So, I use a torque wrench set at 19 ft. lbs. and some anti-seize.

Lichen

I've never torqued a spark plug or a lug-nut in my life. Someday, I'll probably be sorry.

1987C4

Thanks guys! I appreciate the replies very much. I hate to be so paranoid, but I love this crazy car and hope I haven't hurt it. I'm going to head out and check if they have loosened any and shoot for something like 15-18 ft lbs. In the past with aluminum heads, I've just snugged them up and let it go, but this is not just any other car to me. I guess I want to do everything as close to perfect as possible and keep her on the road. Hopefully nothing has loosened up and allowed hot gases to erode the threads. She runs great and I've never noticed any problems, hopefully all is well and just needs a little nudge on the wrench. Again, thanks for the help, I appreciate it. It's great to have friends you've never met, who are willing to give you a hand when you have a question that may seem dumb.
Brad

Lichen

Your question wasn't dumb. Some members may give you some crap, but most of us have the same kind of questions.

tonymax2

The only dumb question is the one you didn't ask!

JrRifleCoach

So what kind of anti-seize is required? I've read that some products will act as an insulator that do not transfer heat.

Is there a special mixture just for spark plugs? Or do you increase the heat range to compensate for the thermal differences?

onedef92

Bad JuJu country, Bawana".

rocco16

Anti-seize compounds are usually a mix of greases and copper, aluminum, stainless steel, molybdenum disulfide, lead, nickel, zinc, graphite, or Teflon.

I've never heard of glass beads being used as a lubricant, or an anti-corrosion additive.

http://www.astinfo.com/

One also has to be aware that many torque values are given for clean, dry threads only. If you add a lubricant to the threads and use the recommended torque value for c/d threads, you can cause damage.

Larry
code5coupe

Mike_88Z51

Very good point Larry! I agree wholeheartedly. That is why I use a torque value of 19 ftlb, which is ~15% less than the maximum and ~5% above the minimum as listed by the factory. One has to take into consideration that the anti-seize affects the final torque results, and that even the best consumer torque wrenches are only guaranteed accurate to 3% plus or minus with 4-5% the standard.

Given a range of 18~22 ftlbs the middle value is 20 ftlb. Allowing for the effect of the anti-seize and built-in wrench inaccuracy, I use 19 ftlb which is roughly 5% over the recommended minimum (dry) value. The anti-seize tends to throw you off in a positive way (tighter than you think) so if the wrench is under reporting the torque by 3-5% (actually overtightening), the two overtightening values combine. At 19 ftlb I have 15% positive leeway which is plenty if the torque wrench is anywhere near spec and I use just a minimal amount of anti-seize as required. If the wrench is over-reporting the torque, then that cancels out some of the inaccuracy induced by using the anti-seize and I'm still easily within the lower range limits given the accuracy of the torque wrench.

VQT88Vette

How do you put a torque wrench on to tighten the plugs should be the next question. It is hard enough just for the regular 1/2" ratchet to fit in there especially #8 plug