i know what the spark plug torque spec (14-22 lb-ft)..but is that a dry spec w/o anti seize? If you use anti seize do we torque it less? i have heard 25-40% less..is this true?

 

Torque the same. You really don't want to use too much anti seize anyway. Just use a tiny bit to put on the threads and that should be fine.

 

Never heard that. Anti seize just allows you easier removal after they have been sitting in there for thousands of miles

 

It's absolutely true in the engineering design sense - dry torque is different from lubed torque. But since spark plugs have crush washers, I think it's not such a big deal.

Dave

 

The axial force in the plug is still the same whether you have a crush washer or not. It just builds up a lot faster as you tighten without one.

Obviously if you are reducing thread friction through lubrication, a larger portion of the work you put into tightening the spark plug goes into increasing the axial force in the plug (The force that tends to pull the aluminum threads out of the head.)

I have had the misfortune of changing the spark plugs in an engine where someone had previously overtightened them. On two of the 6 plugs, the aluminum threads came out in the threads of the spark plug. I ended up removing the head and installing helicoils in all 6 ports. (This was on an 89 Supra turbo)

I see no need to use any sort of lubrication on a sparkplug. Aluminum and steel and their oxides do not readily bond with each other. Therefore there really is no tendency for a spark plug to seize in an aluminum head.

 

I never suggested that the axial force wouldn't change. But it's still pretty irrelevant.

Now that I think more about it, I've heard good advice saying that you should only turn something like one half turn (180°) after you feel the plug begin to meet resistance. This means the crush washer is partially flattened, which is enough to create a good seal. Some people continue until they feel even more torque and smash the crush washer flat - this overtightening is not necessary and can lead to stuck or damaged threads.

Dave

 

I just tighten till they're snug then just a little more.