springer3

I am doing the 12,000 mile service for the first time on a 964. Rennlist member BLK964 came with his super-stereo-equipped tiptronic C2 to assist and get some direction on how to DIY his next service. It was fun getting a ride in a different car, and he got his codes read with the Hammer during a test drive in his car.

I was pleased with how clean the old plugs were after 12,000 miles. Almost like new, but a check with a 0.08 mm pin gage showed there was erosion in the gaps. The threads on the old plugs were dry, and some corrosion was present. It did not "feel" very nice backing out the plugs because of the corrosion. I have always used "Never Seize" on new plugs, but the factory manual has a "do not lubricate" instruction for the spark plug threads. I know lubrication lowers the torque requirement, and you don't want to risk getting conductive paste on the porcelain insulator, especially around the center electrode. I also know torquing a lubricated thread to a dry torque spec can strip the threads. Other than that, I don't know of any downside to thread paste, and there are a lot of benefits (more consistent gasket clamping, less chance of galling, better corrosion protection). I therefore did something I always caution against, and disregarded a factory instruction. I applied a small amount of "Never Seize", and installed the new plugs at 10 ft-lb. That should get the gasket clamped down about the same as the factory's 15 - 22 ft-lb dry torque spec. Anyone think I made a mistake?

The new Bosch plugs were gapped perfectly out of the box except for one which had evidently been bumped enough to close the gap. A standard gapping tool was successful at getting the bent ground electrode back into place.

Bill Gregory

I may be mistaken, however, I thought one reason the factory said years back not to use any lube is that they were concerned with the ground connection between the plug and head.

springer3

I hope that is the reason, because Never Seize contains aluminum and copper particles as part of the anti-galling package. I expect smeared metal particles will improve the impulse impedance.

I was not happy to find rust, because it is abrasive, and over time it will damage the threads. Rust causes friction to increase, and I also was concerned about adequate clamping pressure on the sealing ring.

I test bolts as part of what I do for a living, and we measure torque versus force using specially-instrumented bolts. Lubrication makes a huge difference in clamping force. Rust and other types of thread damage keep bolts from getting tight. Thread paste makes rusty and even mildly damaged threads clamp like new, and the consistency improves. I have always used thread paste on spark plugs, including my previous 911. I have not had a problem.

A word of advice: if you deliberately or accidently lubricate any thread, be sure to use no more than half the dry-thread installation torque. The friction modification from a lubricant more than doubles the tension versus torque relationship. Threads are installed at about half of the damage threshold, so it is possible to do serious damage by torquing a lubricated thread to the dry torque value.

warmfuzzies

Hmm,

I've always used a smidgen on spark plugs and diesel injectors. Being doing it for years, and never had an issue yet.

Kevin.

Matt Romanowski

Too much antizeize can impede the heat transfer out of the plug (causing all sorts of problems), but I would never suggest not using any. Aluminum heads gall all too easy.

Matt

springer3

I went ahead and used paste because I could not bear to put the new plugs back in the threads that still had rust from the old plugs. I was happy to get the old ones out without trauma, and did not want the new ones to get stuck..

"Never Seize" brand (normal disclaimers) thread paste has particles of copper and aluminum that smear when sheared between the mating threads. I think that sort of contact would improve both the thermal and electrical path between the plug and the head.

Thanks for the feedback. I tremble when I go against afactory recommendation. They are seldom wrong. I feel better now.

sonny1

Use it,I have used it on all my rebuilds (20yrs.)and never have an issue with it.Cheers,Sonny.

Dunasso

I've never had an issue with it either; I don't use it. Never saw the need; not for sparkplugs anyway. If the factory says no lube that mens no lube. As long as you take your time, notice when there is or may be a potential problem, then you can take the appropriate steps to prevent a disaster.