What are you guys using, and does it make any difference?
I only use NGK racing plugs, and I have used both styles. No A-B testing, so no idea if any difference in performance. My pistons have very large domes, but they do have a small notch for the plug. I checked the clearance for projected core plugs during assembly mock-up, and it was pretty close. It seems like the engine fires up more quickly with the extended nose plugs, but that could just be perception, it always starts very quick when warm no matter what plug. I suspect the long nose plugs might add maybe a tenth of a point of compression, if someone is searching for every thousandth of ET.
Just really a curiosity. Kind of like indexing the plugs. Used to do that, not anymore, don't know if it made a bit of diff. If I was running Comp that might be different story though...
If I remember right, the main reason for the projected core design, was that they supposedly act like a hotter plug when you would need one, (at low speeds), and act like a colder plug when needed, at higher speeds/intake mixture velocity. But that was done with typical production family cars in mind.
So which style is best for racing? Since you can buy "race" plugs in both styles, it may not matter much?
Your thoughts?

I generally don't run them, but my 632 has a high-speed miss on injected alcohol that I've only been able to fix with projected tip plugs. Doesn't do it on gas.

I feel like the problem is cam duration-related but for now the plugs fix it.

Logic suggest it's better to have the spark out in the chamber where it is un-shrouded and the tip can stay cleaner. The same can be said for indexing. If your ignition is up to par and you keep fresh plugs then it likely won't matter. However it might provide a margin of error that would be nice to have for "free".

Good point, C.V. I read long ago, a story in an issue of Super Stock/Drag Illustrated, (my favorite mag, wish it was still published), that one "pop" of a misfire could slow a Super Comp dragster .006-.010, depending on where in the run it happened. Keep in mind this was probably early 90's, so maybe not as much effect with today's big-inch, high-hp motors like Tony's 632. (Or maybe more)?
Margin of error for free is a good thing, as you said. My biggest problem is finding the time to do the little extras I used to.

My pistons will close the gap on a projected tip plug, been there done that. Indexing doesnt help either, I tried it.

quote:

Originally posted by Hetzler:
My pistons will close the gap on a projected tip plug, been there done that. Indexing doesnt help either, I tried it.

Which goes along with what I was about to say.

Use projected tips if they don't hit your pistons.

I would never run extended tip plugs in anything with good compression or intended for high RPM's.
Mostly a plug durability issue.

quote:

Mostly a plug durability issue.

Please elaborate.

Core and nose fracturing seemed to be an issue.

quote:

Originally posted by Woody B:
Use projected tips if they don't hit your pistons.

That's also my best suggestion. I use standard NGK plugs. They all have to be indexed to keep the piston from hitting the ground strap. I doubt an extended tip will work on my engine.

WE use them a lot, sometimes making room to fit.Years ago dyno testing we put a .750 reach plug in a .500 head.,cut threads back .Made 10+ m,ore HP.Bill C.

not to highjack the thread, but is really a big deal to index your plugs if your pistons have reliefs in the domes for the electrodes? I normally do, just wondering if really makes a difference?

Typically BBC's with large domes and especially on alky like extended tips. If you got a good piston it should have a plug notch so they won't hit the plug but many do hit so you need to index them. On gas, many just use the regular tips so they don't have to worry about them.
With NOS, you should not run an extended tip plug. Small shots shouldn't really matter but with the added power comes added heat and the extended tips can get to hot and cause detonation. This could be one reason BC BBC motors respond well to extended tip plugs since they take longer to cool vs reg tips!

As for indexing plugs goes for power, the more power up make the harder it gets to light it! So anything you can do to help light the fuel/air mixture the better, such as reducing plug gaps. Indexing plugs is easy, take no time to do it and will never hurt performance so why not. But for most typical bracket combos, you'll likely won't see any difference.

Since several have mentioned indexing the plugs, is there any standard orientation of the ground strap that is most favorable? Does anyone have any information from reputable source(s) who have done any dyno testing with the plugs indexed at various positions? I know some have to index for clearance, but I am asking with regard to performance, (improved power, or simply a more reliable firing of the fuel)? I've heard and read different advice, ranging from put the strap toward the head/away from the center of the chamber, to point the open side toward the exhaust valve, to centering the open side between the 2 valves... When I was doing it, I was just trying to keep the strap out of the way of the fuel charge/flame front, up toward the head surface. Which on a BBC was close to a 45* angle on an installed engine.