Way back I remember reading GEE PASTA’s post about how open side's of the plugs should be open to the exhaust valves in order to possibly being able to run more timing. Everywhere else I read that open side of the plugs should be open to the intake side of cylinder. So which one is it or it doesn’t matter at all? Thanks

 

I tried to link the page but its not working... here's a brief explanation of indexing plugs (from the site I was trying to link):

What Is Indexing? /
Generally speaking, the idea of indexing is to position the spark plug so that its gap is facing the center of the cylinder, angled slightly toward the exhaust valve—the most common arrangement. (Some engines work better with other gap locations.) This is important because, as the piston approaches TDC, the air/fuel charge is being compressed. The charge or "mixture" is being forced toward the area of the spark plug—and normally, the exhaust valve. The true speed of this force inside the combustion chamber is extremely fast. Some experts speculate that it surpasses supersonic speeds.

Because of this, the spark generated from the plug should be in a "position" to create the best possible flame front. Looking at a typical side-gap spark plug, you'll note that the electrode can actually block the flame process. On the other hand, if the electrode gap faces the on-rushing air/fuel charge, it stands a much better chance of igniting a flame front.

How To Index:
How is a spark plug indexed? Simple: Mark the spark plug insulator body with a felt marker (never use a pencil, which acts the same as a carbon track inside your distributor cap) on the side where the ground electrode attaches to the spark plug body. Instead of rummaging through boxes of spark plugs to find the elusive combination of perfect plug threads that match the cylinder head threads, use indexing washers. These soft copper washers are available from the aftermarket and will fit both flat- and tapered- seat spark plugs. They're available in three thicknesses: 0.060-inch, 0.080-inch and 0.100-inch.

Copper's inherent softness along with the various washer thicknesses make it simple to thread the spark plug into the cylinder head and tighten it to the point that the index mark is situated in the correct position relative to the combustion chamber. (Never double up washers; they aren't intended to be used in tandem.)

Power Gains:
Real-world power gains vary. Some engines or combinations respond differently than others. In fact, all engines will pick up power, but some gains will be more dramatic than others.

In the end, it can't hurt to index the spark plugs. This can contribute to superior engine efficiency and improved economy.

 

Wow, I never thought I'd see the day that someone on a forum actually discussed, cared, or even knew about indexing plugs.

Thank you OCG35 for posting something intelligent that actually matters rather than the usual drivel that gets posted on forums.

Someone should sticky this thread. I'd love to know if anyone with an engine dyno can confirm which orientation helps the VQ motors most NA and FI.

 

OCG35, I saw that article by Wayne Scraba/autoMedia.com on this page at the advanceautoparts.com site. There is also interesting study on SAE.org site, Experimental Study on Spark Ignition of Flowing Combustible Mixtures which states:

The results reveal the important role that both the flow phase duration and the flow phase current play in the ignition process. It was also shown that the preferable law of energy release depends on the spark gap and spark plug orientation, in particular under high flow velocities (7-9 m/s). The crossflow plug orientation was found to be preferable in the entire range of experimental conditions. The upstream plug orientation is better than the downstream one at low flow velocities, but the trend inverses at high flow velocities. There is an optimal range of flow velocities across the spark gap for minimum ignition energy. In our experiments a flow velocity between 5 and 8 m/s was found to be preferable



Wouldn’t chassis dyno, which you have, also show results? Please let me know if you need my spark plugs
BTW, who is the one posting with UpRev member id these days? Thanks

 

Wow, I have never thought about that. I'm going to change my plugs soon, can't hurt to do it.

 

Chassis Dynos have an error rate of up to 8% by nature. You wouldn't show repeatable honest gains in that tolerance. Your difference in power could be attributed to anything, temperature, oil viscosity, barometric pressure. You need a proper engine dyno with a more controlled environment to test factually the difference in alignments of the spark plug.

 

+1,000,000 That was the best post have seen in some time. Goo werk OCG35!

Very interesting subject I will try it next time I get to the plugs. Thanks OP

 

Just to be clear… I didn’t do that write up. As stated in my post, I tried to link the site that had the article (twice) but it wasn’t working, so I copied it here…

I know what the OP is referring to though regarding Pasta’s old posts… I’ve talked to him a few times (in threads) about indexing – so its not something I’m unfamiliar with… but I didn’t want the misconception that I wrote that.

I haven’t bothered to get indexing washers yet (planned to, but never got around to it and have had waaaayyyy to many other project on the car over the past couple years) – eventually I will though. Initially I thought you would need a bunch of plugs and would need to go through them all hoping to find the ones that will face the right direction with the proper amount of trq… but found later (as the article states) that indexing washers are available to make to task much easier/more convenient... Pasta is the only one I know of (in G family) that even indexes his plugs.

Anyway – glad you guys got benefit from the post