Indexing Spark Plugs

[bk2001]

Does this actually work and how to on a Vibe?http://www.advanceautoparts.co...p.aspIt sounds like it makes sense, but which way to point the ground electrode?

[BobofTheVibe]

Well, it depends on the shape of the combustion chamber. So, a cross section of the head would be a good place to start. I would think where ever the most 'mixture' would be would be the best place. Edit: I found the SAE development papers for the 1ZZ-FE, which is just interesting to read anyways, it looks as if the combustion chamber has a pretty steady dome with an even shape with no real biased. Reference page 5 here: http://www.spyderchat.com/1zzfe.pdf So in short, I do not know where to point the electrode. Looks like Toyota may have gotten it right to begin with - just an opinion though.

[djb383]

Won't do much of anything...........the Vibe's a 4 valve/cyl HEMI and the plug is in the center of the combustion chamber.

[BobofTheVibe]

I would almost certainly agree with djb, the only thing I would want to see before making a decision for sure is the design of the top of the piston - since it may bias things slightly. However, since the difference can't be that drastic I would think a power increase would not be that great. Indexing is a really good idea when we are talking about a 'wedge' style designs. However, djb is right our flat topped hemispherical combustion chamber design makes it not all that useful to index spark plug - since one position should be almost exactly equal to another. For standard designs of combustion chambers in heads I would recomend this site: http://www.secondchancegarage.com/public/585.cfm

[djb383]

+1 for plug indexing with 'wedge' style heads, ie., push rod OHV style heads/engines, not DOHC/SOHC hemi heads, like the Vibe.

[BobofTheVibe]

Yeah, it would be a strange head/engine if it was wedge. It seems as if head design is a Texas specialty judging by the posters.