Indexing sparkplugs 4A-FE - Toyota Nation Forum : Toyota Car and Truck Forums

}{ead$hot Zod · 08-26-2009, 11:36 AM

What is the best way to index the sparkplugs? Center of the cylinder (facing down toward the piston dome) or slightly angled, facing the exhaust valve?

Donald · 08-26-2009, 11:51 AM

I have never heard that term before. What is indexing a spark plug?

}{ead$hot Zod · 08-26-2009, 12:07 PM

It's an old term (I'm 42) for positioning sparkplugs not only in the same direction but also for optimum flame propagation. Think about the flame if the open end of the electrode faced the injector. Part of the flame would hit the back end of the electrode. Its only good for 2-4 hp (back in the day) but it's free and better for torque and emissions. Every little bit helps. Hypermilers would benefit from it. Also some people will use copper indexing washers to back the plug out just a tad. The cheap and easy way is to use a sharpie marker on the side of the open electrode and just make sure each plug faces the same direction.

indexing plugs

Flashmn · 08-26-2009, 12:13 PM

No use... the toyota head causes the fuel air mixture to swirl. old side valve V8's were another thing.

}{ead$hot Zod · 08-26-2009, 12:19 PM

thanks, this is my first 4 banger.

Donald · 08-26-2009, 12:22 PM

Quote:

Originally Posted by }{ead Zod

It's an old term (I'm 42) for positioning sparkplugs not only in the same direction but also for optimum flame propagation. Think about the flame if the open end of the electrode faced the injector. Part of the flame would hit the back end of the electrode. Its only good for 2-4 hp (back in the day) but it's free and better for emissions. Every little bit helps. Hypermilers would benefit from it. Also some people will use copper indexing washers to back the plug out just a tad.

indexing plugs

Ok, gotcha.
I have 10+ years on you, but I have never heard of it.
Mind you, I haven't hung around performance engine builders much.

I can see the theory of it, but it seems so technical, it would require some extreme R&D to figure out the right angle to set them at, as it would probably be different for each different engine design.

I'll have to ask my local Toyota specialist/racer to get his opinion.

}{ead$hot Zod · 08-26-2009, 12:32 PM

here's a decent read on it from the Hot Rodder's forum. Only 2 pages but lots of different theories about it.

http://www.hotrodders.com/forum/inde...ugs-79782.html

Donald · 08-26-2009, 04:12 PM

Quote:

Originally Posted by Flashmn

No use... the toyota head causes the fuel air mixture to swirl. old side valve V8's were another thing.

Ok, I never knew much about V8s.
I guess you posted while I was writing my previous post.

Flashmn · 08-26-2009, 06:22 PM

Older V8's were designed half-assedly, thats why you get serious gains on everything you do on them. No wonder summit racing sells headkits for 3000bucks which increase power alot. Youdont see that with the run of the mill japanese engine.

Ghostyman · 08-26-2009, 07:08 PM

Quote:

Originally Posted by }{ead Zod

What is the best way to index the sparkplugs? Center of the cylinder (facing down toward the piston dome) or slightly angled, facing the exhaust valve?

This confuses me. If you index conventional spark plugs, the gap is always pointing to the side of the cylinder. How could it point down?

Most engine benefit from pointing the gap towards the intake valves. If the plug doesn't sit in the middle of the combustion chamber, you'd want it pointing at the area with the largest volume.