Spark Plugs

[cmcfaul]

at that high compression I would go with a very cold plug, very high octane gas and try to keep temps low. Detonation is hard to feel but will cause the compression ring to be eaten by the engine (just gone). I am a fan of iridium plugs (bigger spark).

Chris


The piston valve relief broke and there is no ring under there (engine ate it due to detonation)

[E Sully]

Originally Posted by flightlead404

Why no anti-seize?

I'm curious about the comment here and in other places related to Porsche engines and the recommendation to not use anti-seize.

I've regularly used anti-seize in all my oil cooled engines, aircraft, NA, and turbo 911's for 30 years. In the past I used the silver paste type, although recently I've gone to a high quality aircraft copper based anti-seize.

I've never had a problem with ignition due to poor grounding of the spark plug, I've never had a properly torqued plug back out, and I've also never damaged any threads from galling or other issues because I use anti-seize.

I'm careful to not get it on electrodes or on the first few threads on the nose of the plug.

Why the recommendation for no anti-seize?

Originally Posted by Neil Harvey

Because anti seize is more often used in excess. It changes the heat range of the plug as it acts as an insulator. Not to mention, when used in excess, it can get onto the insulator showing as if the plug is overheating.

You are partially correct, contamination can occur, but no issue of acting as an insulator.
NGK on it's web site has stated that the main problem with anti seize is that they have found it tends to cause people to over torque the spark plug. New spark plugs come with an anti seize material on the threads, so no additional compound should be used. Adding anti seize reduces friction and can cause stripped threads when using the original recommended torque values. They recommend reducing torque values by 30% when using anti seize paste.
https://www.ngk.com/learning-center/article/522/plug-torque-settings

[Trackrash]

If the last set of NGK plugs I bought had anti seize on the threads it was invisible.

I will say that they changed the crush washer on the plug. I found it impossible to tell how tight it should be.

NGK used to state on their site, that the plating they use is an anti seize? Really?

It looks like NGK has backed off on that and now are OK with anti seize, but the torque value is less.

They mention 1/2 to 2/3 of a turn after the gasket touches. Now that makes sense.

To all you guys putting your plugs in dry, you will be OK if you change them often, otherwise good luck IMO.

[Neil Harvey]

Anti seize actually does change the plugs ability to remove heat from its body. We have seen this multiple times. I think you have understand each application. Air cooled heads act very differently with plugs. It is always assumed that plugs are torqued each time.

[Neil Harvey]

I should have been more clear. I am speaking more about high performance and race Porsche 2V air cooled and race engines. These run higher head temps from running at WOT a lot more than street engines do.

[Trackrash]

Originally Posted by Neil Harvey

Anti seize actually does change the plugs ability to remove heat from its body. We have seen this multiple times. I think you have understand each application. Air cooled heads act very differently with plugs. It is always assumed that plugs are torqued each time.

Correct me, if I am wrong, but my take away from this is if you are using anti-seize on the plug threads, us it sparingly and consistently.

[Neil Harvey]

Originally Posted by Trackrash

Correct me, if I am wrong, but my take away from this is if you are using anti-seize on the plug threads, us it sparingly and consistently.

Yes.

But if you feel the need to add anti seize, do it sparingly. Just a very small amount on the threads and wipe the excess off so it is only in the root of the threads.

The installation of plugs starts when rebuilding the heads, making sure the threads are in good condition. Heli coiling the threads changes the temp range too, so be careful.

NGK and some other brands require no additive to the threads. Plugs should always be installed using a "rubber" by hand. I still have one and use it today, I used in my F1 days. Then use a torque wrench to tighten.