sparkplugs

[Paul Workman]

Originally Posted by rush91

For us un-mechanical folks, what am I looking at? Spark plugs obviously, but are these good looking plugs for a year worth of use? Were they fouled or anything, and what does gapping do? I'm wanting to change my plugs, would they need gapped or is that for modified engines?

As ssrzz4 said: "Near perfect". My point is you don't have to go to some exotic, pricy plugs for good performance. These plugs are inexpensive (about $2 ea.) perform extremely well (as Pete's car and photo demonstrates).

These plugs could easily do another 3-6k miles (like last season), but plugs are so easy to change on an LT5, one could put in a new set each season (as I usually do).

The space between the electrodes is the "gap" which the electrical charge must jump resulting in spark that ignites the very hot, compressed air/fuel mix.

The gap can be increased or decreased by bending the (prong) electrode closer or further from the center electrode.

The amount of gap is a recommendation that comes from various sources. But, generally the larger the gap, the longer and hotter the spark. A feeler gauge (you should invest in one, btw) is used to measure and set the initial gap; which increases with use with mileage and other conditions.

Difficulty in reaching/replacing the spark plugs on some engines, and with the demand for longer maintenance intervals. resulted in the recent use of exotic rare earth materials. These plugs offer the advantage of increased durability (longer change intervals) AND significantly larger spark gap which results in a hotter spark.

So, why not use exotic plugs and reap the benefit of "hotter spark" and longer life?

Well, plugs work best when new, but their performance begins to deteriorate from the first moment they are put to use. Changing plugs every season means my plugs are always near the top of the performance curve for the entire time they are in the motor. And, it "forces" me to check how the motor has been running for the past 3-4k miles or so. (Rare earth plugs may go "50,000 miles" before performance deteriorates to the point of changing them out of necessity. But, why put up with marginal performance near the last 1/3 of their life...maybe 20k miles or more?)

Not trying to sell you on plugs. Use whatever you think is best. But, my (500+ hp) motor obviously likes the plain ol plugs I'm using, and the video of Pete's car doing an 11.3x quarter mile does too. (BTW, that video is old: since then he's cut an 11.04 sec quarter with that stock-bottom 350 LT5 using those 41-602s!) Point is: you don't have to spend an arm and a leg for good plugs...unless you want to.

[secondchance]

Originally Posted by Paul Workman

you don't have to spend an arm and a leg for good plugs...unless you want to.[/I]

I just want some iridium on my car. That's all...

I use to run AC Delco Rapidfire when these were copper plugs with fluted electrode. LT5s ran great with these plugs and these were good for 12,000+ miles. Somewhere along the line, GM kept the name but changed the plug design. That's when and why I went to iridium plugs. Iridium plugs are pain because when you gap them you can easily damage the electrode if not careful unlike conventional plugs.

[mike100]

Originally Posted by Paul Workman

...

The amount of gap is a recommendation that comes from various sources. But, generally the larger the gap, the longer and hotter the spark....

'longer' in distance jumped by the spark, but the burn duration will be shorter in time as some of the energy was used to jump a long air gap. old fashioned automotive analyzers used to have inductive scope pickups for wires and triggered off the coil negative. It was a pretty cool way to look at some before and after on ignition tune ups or mixture problems.

An electrical spark will jump a bigger gap in a vacuum vs sea level and going to pressure extremes, high compression or turbo cars usually run narrower gaps to insure proper light off....either that or hotter ignition systems.

[XfireZ51]

problem w increasing the plug gap is that it puts a strain on ignition coils.
The LSx coils have the additional uumph to jump a larger gap like .050".
At that gap, I found that my motor idles more smoothly but high rpm operation could suffer.

[Hib Halverson]

Originally Posted by Dynomite

For my 91' NGK Iridium BKR5EIX Eagle

Car must be a total waxer.


Even the LT5 plug called for by ACD back in 90, the FR2LS crosses to the NGK 6 heat range. The NGK 5 heat range is like putting an FR3LS into the engine, which is one range hotter than what the book calls for and two ranges hotter than the heat range Lotus specified during development.

[XfireZ51]

Hib,

I'd been using NGK6E for quite a few years, but recently went to NGK5E after inspecting the ground strap and doing plug cuts. The 6s were just a bit too cold for my setup.