Lone Ranger

I've never indexed plugs during installation, I just screw them in and torque to spec w/ my clicker.

I'm not sure I could see the #8, #7, and #6 plugs well enough to line up the mark on the insulator w/ the exhaust valve approx. location anyhow :crazy:

Curious is anyone take the extra pain to do this, considering how much of a task changing plugs are already on C4's.

It would be nice if there was a universal thread indexing used on all heads and plugs that would line up the plug gap well 'automatically' when torqued to spec!

Z06_BluByU

on the drag car... not the vette.. :steering:

ToniH

What?....no but I check my tire pressure every 5 miles to make sure they are correct.... Just kidding...no I don't ;)

TH

DarkHalo

My last fun car, a 72 elco that I street raced every weekend yeah, I indexed them...but I also had enuff room to stand next to the engine to work on it too...needless to say that aint the case with the vette. Like you said the passenger side front ones are SOBs at best. :blueangel:

FlyboyZR1

What is indexing? :confused:

Nathan Plemons

There is a theory and a rather correct one that there is some amount of power to be gained if the sparks plugs are installed with the gap facing a certain direction. Indexing the plugs means that you take the time to figure out which direction this is for each cylinder and then marking the head and the plug. Then you install the plug as usual, you just tighten it a little more or a little less, whatever is needed to make the marks align.

For a street car with a cramped engine compartment like the vette it's a fairly futile effort because the work involved really wouldn't be worth it. On an all out race motor where you need every last bit from the engine then it's worth taking the time.

h rocks

I tried on the Vette, but it's just not worth the aggrevation. Unless you had the heads off, and could mark everything and "PRE-index" a couple of sets of plugs in advance, it's a nightmare.
I did however do it on an MR-2 ricer that I had in the late '80s. On that little twin cam four banger, it really made a difference. It was hard to believe frankly. But when you're only starting out with 135 HP, it doesn't take much of an actual HP gain to make a fairly large %age change in HP.

Lone Ranger

Nathan, you seem to know LT1 heads. Which direction should the plug gap face in an LT1 head for best results?

Dan Parker '96

Indexing a plug normally means lining up the open face of the plug towards the exhaust valve. The ground strap would then help keep the intake charge from "blowing out" the spark.

This only applies to engines that can move extreme volumes of air. It will do nothing for a stock or mildly modified engine.

BILLY D

Dan: I thought the open face of the plug faces the intake valve so the gas charge gets the full potential of the spark and is not blocked by the ground strap. This is how I index the plugs on my Harley, only because its easy to do. On the Vette its to hard.

Dan Parker '96

Well, looks like "indexing" is definitely open to interpretation.

Here's a Harley view (open spark towards intake): http://www.nightrider.com/biketech/h...s_indexing.htm

Here's a Ford view (index towards center of combustion chamber): http://www.fordmuscle.com/archives/2...gs/index.shtml

Here's one that says index slightly towards the exhaust valve: http://www.automedia.com/xml/pht/pht20001001sp.xml

And finally.. Here's NGK saying that it's not possible to determine without dyno tuning (scroll down to Indexing)... http://www.ngksparkplugs.com/techinf...s/techtips.asp

I guess we are all correct :)

Z06_BluByU

:withstupid: :steering:

Nathan Plemons

I don't have the slightest clue. So what I do is install all 8 and torque them down until my calibrated elbow tells me it's tight enough. This way all 8 are probably different and maybe one will be correct :D

BILLY D

Dan: I never knew there were so many ways to index a plug. I first learned about it from a Harley tech artical and thought it was that way for all engins. The artical said to do it the way I stated and it sounded good to me. Live and learn. Thankx Billy D.

corvette-pilot

I also thought it was the opening towards the intake charge. Don't see how aiming it towards the exhaust would do any good??

Also agree for the gain you might get it isn't enough to beworth the BS/trouble

Lone Ranger

But I can feel the perfectionist in me getting restless :rolleyes: I bet I find myself trying to index my plugs next time I'm bored with nothing better to do :crazy: