45 years ago when I owned my last air cooled four cylinder engine we used to mark the spark plugs so you could “index”, align them in the plug hole to fire in their hottest direction, usually away from the electrode ground.You would index them to fire across the cylinder head. I assume today with the new electrode configurations there is no need to index any more.
?
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Interesting ! Never heard of this. How was this supposed to be better ? Do mean that the ground electrode (the welded side) faced toward the closest proximity of the combustion chamber ?.................Bruce
Bruce,
Lots of info and products out there just search "spark plug indexing". You can purchase washers so the tightened sparkplug "faces" the right direction. Its best to have the "open: side of the plug face the inlet valve. I was wondering if it was still practiced on VW engines.
OK...Got it.....I'll check it out.....Thanks Mr. Thorpe.....Bruce
I have been involved with VW aircooled engines (and the hotrodding end of it) off and on for 45 or so years now (a '66 Beetle was my first car in 1974 and within 3 months of purchase we'd put a Holley 2 barrel, 009 and Treuhaft extractor and glasspack on it) and this question/argument/debate has been a topic since before I got involved. For street level performance no one has ever proved it was advantageous. A high strung racing engine on the ragged edge may be another story, but again, I don't recall anyone ever definitively proving it's worth doing. I'm not saying it isn't- I just don't remember any data or dyno tests to that end. Al
66 was my first car 1970, we all wanted to hot rod our cars but never had enough money so we did things we thought would help and be cheap like plug indexing, it was a real pain for a teenager to do and we were never sure the plug was indexed correctly or not, but we always thought it made us faster 
We did put out for headers and a glass pack from Empi.
Richard
I used to do this on my HD shovelhead. I was told that if the “open” side of the electrode faced toward the piston it would fire into the air / fuel misfire and burn more completely.
