I keep hearing all these people who cut back the ground electrode on their spark plugs. Sounds like some kind of gimmick to me. Here are my reasons, not trying to flame anybody, I'm just trying to make sense out of it.

By cutting back the electrode you increase the plug gap. Alright you just re-gap the plug. Still you have an electrode that is only anywhere near one side of the center electrode. Meaning that the spark is going to jump from that one side of the center electrode over to the cut back plug. Before long you wear down the center electrode on that one side, only now can it begin to fire over the rest of the electrode, but your gap is increased again. Now however you cannot re-gap your plugs because there is not enough electrode material to get them close enough together.

Maybe it's just me, but it sounds like this follows the same logic as sanding off about half of your brake pads or clutch before you install it. Maybe I'm missing a key point, that's why I'm asking. Somebody please explain it to me.


[Modified by Nathan Plemons, 8:11 AM 11/1/2001]

 

anybody? I know many of you do this. I'm honestly curious about the benifits?

 

Hey information is gained through discussion and argument, i.e. a forum.

Anyway, you raise valid points. I got this "tip" from two sources (Myron Cotrel & Dave Emanuel); from a power gain standpoint it worked as advertized. The principle is to expose the mixture to more of the flame font to get more efficient combustion.

The plugs in the Vette had opened from .045" to .050" in a little over 1 1/2 yrs, which was still within the range of my ignition system. Still, I regaped them by bending the ground electrode slightly. It looks like the trade off is plug life vs the power gain. However I've been running cut-back spark plugs in the IROC LB9 for over 4yrs and in the Vette L98 for 1 1/2 yrs so can't recall how plug life compares with stock configuration (memory is the 2nd thing to go).

 

yup, what he said.

 

I would not do it. I've heard complaints about "engine miss" after this has been done. Just another gimmick or someone who is bored and can't leave well enough alone. IMHO

 

anyone have pics of this done? maybe i am slow but even after having this described to me i still can't visualize it :confused:

 

You can cut the electrode so that 1/2 of the center is exposed and get pretty good mileage out of the plugs. Try using autolite platinums for this. They are cheap and will last longer because of the platinum center. Take a close look at AC Rapidfire plugs. You'll find that the electrode stops right at the point where the center electrode starts to taper down.

 

There's a pic on my site of an example though not one of my plugs.

 

When you cut back the electrode you can still keep the same gap. This procedure just causes the spark to be fully exposed to the cylinder instead of being shrouded by the end of the electrode. I did it to my car and haven't experienced any miss or any other trouble at all. :cheers:

 

the +4's work on the same principal. If the center electrode wears on one side the spark will move to another ground. (path of least resistance) I checked the gaps on several of my plugs when installing them and the gaps were virtualy the same. Cutting the plug is an old hot rodders trick that I first heard about in the early sixties. I had forgotten about it until I read about it on the forum. This is why I decided to try the +4's. I'm happy so far.

 

this is an old old trick, dyno testing has documented a consitent 5-8 hp of a typical sbc, its in many of my hot rodding books, and i plan on trying it when i get some cut off wheels for my dremel

 

I would have to see it to believe it. I am skeptical about any hp gains. If anyone had a dyno of "before" and "after" I would love to see it. Or a copy of the hot rodding article would be interesting.

 

I just cut a set of TR55s. Left some overhang so they gapped right. These replaced the OEM plugs that had 23,000 on them.

Put it on the scanner before and after. No primary/secondary misfire before - lots of it reported after. Car did not seem to be missing - just detected by scanner.

I mentioned this a while ago along with the info that a friend had a lot of missing reported on his scanner with uncut NGK plugs. Got flamed for saying something negative about NGK and a comment about what do you expect with cut plugs etc.

Just changed to uncut TR55s and guess what. Still reporting mucho misfires. Car seems to run just fine. I don't think the fact that the PCM is reporting misfires means that an actual misfire is occuring. Has to do with some vodoo related to the crank sensor and may be related to the resistance in the plugs.

Like I said, the car ran fine with both cut and uncut TR55s - just indicated missing on the scanner.

For those of you with scanners, it is not reporting misfires in specific cyllinders - just the primary/secondary counters.

All in all, I don't think the cut plugs are worth the effort. Not worried about the TR55s either - car runs good. I'll probably try another brand next time and see what happens with the misfire situation.