Projected nose plug caused ?

[Tom68]

In past experiences, extended reach spark plugs do not last very long in engines that are run at long periods of Wide Open Throttle.

Drag Racing or other type racing where wide open throttle is limited to short bursts, they seem to be just fine on those plugs but, with engines used in land speed engines or offshore type boat racing and such, the tips go away and won't last for whatever reasoning.

WOT heavy mud, deep sand, high speed, long stages, 4wd, the projected nose plugs were meant to be changed.

[Tom68]

How close was the strap to the top of the piston? I have seen the spark jump to the piston if too close. And what was the gap when installed new? It looks like you had a very good ignition system to arc that large of a gap. Remember as the gap increases the KV of the spark increases, more voltage more energy more heat. I don't know about what everybody else does, but on a performance engine, I like .032 to .035 gap on plugs. The .055 to .065 gaps on newer stock engines as mentioned are not that good for WOT performance. And all you need is enough spark to light off the mixture, over building ignition and gaps in my experience does not get you increases in performance. Large KV loads on ignition components also reduces their lifespan. When working on stock vehicles with coil on plus systems for example, almost every failed coil I have seen is hooked to a 150,000 mile spark plug with a huge gap. If you hook a scope and measure the amperage draw of the coil before and after it is easy to see why the coil burnt up.

Can't answer all that, but yer, the 20 year old LS coils obviously did a stirling job ( since the motor still starts and runs after all that with those plugs) the coils will be going in the bin now though.

[mag2555]

There is no color change over point that can be seen on the ground electrode of those plugs.

That should be seen to take place about half way along the ground electrode if your running a plug with the needed heat range, yours is way the heck up onto the main body of the plug!!!!!

If there ever was a clear cut sign of too much heat going on for the many resons that can take place, then your plugs are a unfortunate example of it!

[Walter R. Malik]

In past experiences, extended reach spark plugs do not last very long in engines that are run at long periods of Wide Open Throttle.

Drag Racing or other type racing where wide open throttle is limited to short bursts, they seem to be just fine on those plugs but, with engines used in land speed engines or offshore type boat racing and such, the tips go away and won't last for whatever reasoning.

WOT heavy mud, deep sand, high speed, long stages, 4wd, the projected nose plugs were meant to be changed.

Within an Offshore Boat in a race you probably can't stop in the middle of that race to change spark plugs but,
I guess you could try one engine at a time ... LOL.

[Tom68]

In past experiences, extended reach spark plugs do not last very long in engines that are run at long periods of Wide Open Throttle.

Drag Racing or other type racing where wide open throttle is limited to short bursts, they seem to be just fine on those plugs but, with engines used in land speed engines or offshore type boat racing and such, the tips go away and won't last for whatever reasoning.

WOT heavy mud, deep sand, high speed, long stages, 4wd, the projected nose plugs were meant to be changed.

Within an Offshore Boat in a race you probably can't stop in the middle of that race to change spark plugs but,
I guess you could try one engine at a time ... LOL.

Changed before the vehicle went to the event that is.

[Walter R. Malik]

WOT heavy mud, deep sand, high speed, long stages, 4wd, the projected nose plugs were meant to be changed.

Within an Offshore Boat in a race you probably can't stop in the middle of that race to change spark plugs but,
I guess you could try one engine at a time ... LOL.

Changed before the vehicle went to the event that is.

Of course but, when the extended tip burns away half way through the event a whole bunch of power is lost.
This happened about half way through the 5 mile run at Bonneville, too.
These places of continuous Wide Open Throttle were where my conclusion was drawn.

[Tom68]

Two cylinders affected, bearings good, Pistons and bores not so much.

20221030_172639.jpg

[allencr267]

Both end, usually the hottest, cylinders?
Thanks.

[Tom68]

Both end, usually the hottest, cylinders?
Thanks.

That's the funny thing, 4 and 5, going to CC the heads since it's the corresponding chambers.

[Tom68]

Don't blame the projected nose, it's still only two cylinders affected, but that's not so important now that I've checked the heat range and it's hot hot hot. There's only one hotter before you reach the fires of hell.

The plug is a Bosch r6 hr9lpp22y.

Heat range.jpg

Pictured next to a plug out of my wifes car.

20221101_145206.jpg

[F-BIRD'88]

Which is the whole point of the non-projected tip style spark plug.. Shorter heat path runs cooler.

[BLSTIC]

Not quite. The comparison with these two plugs if they were photographed level would show similar projection but a much shorter heat path.

I'm looking at finding a projected nose cold plug as a way to reduce ignition advance requirements in a dirt track with a bolt on turbo installation (one of these days), so this thread was a good read.

[Tom68]

Heat range aside, I still worry about the long ground electrode.

[allencr267]

...worry about the long ground electrode.

If those plugs are sticking out as far as it looks from the carboned up threads, I'd worry too, but a bit more about why those 2.
Are they really that exposed?
There are some shorter reach, .700" & 5/8 I believe, or use a washer/s, and that'll let the head suck all that heat out of it, a lot better dissipation wise.
Good luck.
////
Also, how'er the others doing? Intake system/injectors look unbalanced, clogged, vac leak, whatever??
Compression wet&dry.

[Tom68]

...worry about the long ground electrode.

If those plugs are sticking out as far as it looks from the carboned up threads, I'd worry too.
Are they really that exposed?
There are some shorter reach, .700" & 5/8 I believe, or use a washer/s, and that'll let the head suck all that heat out of it, a lot better dissipation wise.
Good luck.
////
Also, how'er the others doing? Intake system/injectors look unbalanced, clogged, vac leak, whatever??
Compression wet&dry.

No, 243 heads, no chamber work around the plugs, length fitted correctly, they just got Hell Hot from the preignition that they caused.

I've run long reach surface discharge 3/8 of an inch into the chamber on a street SBC (threads turned off ) no problems.