spark plug indexing

[akadeutsch]

I found a set of indexing washers for under 20 bucks on Summit. Is it worth 20 bucks to index my spark plugs?

[the grey ghost]

Its a science that I'm not an expert in, but I believe it has to do with the combustion chamber shape and valve orientation, but for 20$ id do it too

[IH 392]

They index plugs in REAL race engines so the pistons don't hit them.

[FlyinRyan]

I wouldn't bother.

[akadeutsch]

Apparently there is a lot of different opinions here. One thing that jumps out at me is the fact that every time you add an indexing washer to the Spark Plug you are effectively changing the C/C Volume by cc's at a time. This changes CR and all that math and machine work you did goes right out the window. Unless you think ahead and save time ccing your head by simply adding washers to increase CC volume instead of removing material. Also, if you find that you have cut too much off of either your head or your block to tighten quench you could always add these washers to lower Compression.
So I guess if you were going to index your plugs then ideally you would want to do it before you cc your Head. I did not index them first, but I have put a lot of time into making my CC the same size so I think I will hold off on adding any washers. I have come across quite a bit of information on indexing and it would appear from my research that leaving the plug open to the intake port promotes the best burn.

[akadeutsch]

Here is a good article that I found on the subject. And our head design sounds similar to the one used here.
http://dodgeram.org/tech/gas/spark_plug ... dexing.htm

[SilverXJ]

Indexing is done to a) change the orientation of a plug to point in a specific direction (typically intake or exhaust valve), which varies and b) to provide clearance between the piston and plug. If you are looking for every little bit of horse power indexing may help. However, the results will be small and only really measurable on an engine dyno.

For our builds it is a waste of time.

As far as changing the CC its so small it won't matter any.

[jeepxj3]

I have come across quite a bit of information on indexing and it would appear from my research that leaving the plug open to the intake port promotes the best burn.

That's what I remember reading, 'plug open towards the intake valve'.