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I've run Bosch, NGK and Autolite in mine and can't tell a whole lot of difference as long as they are a platinum plug. I run an MSD 6 ignition/blaster 3 coil which seems to like a platinum electrode.
 

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Takes you picks.

Hottarod, you can cut back the lateral (grounding) electrode to get the same firing and get a slightly better light-off too. Takes about 10 seconds with an angle grinder, or I prefer a bench grinder. Save some bucks and change them more often. I use plugs like candy - if in doubt, throw 'em out. Sure, you can torch them to burn off carbon and stuff, but at 99¢ each, it's not worth the time or trouble to me unless I don't have replacements.
:tup:
David

A factory cut-back plug for racing on the left. You can do your own, prying the strap up (to avoid hitting the center electrode), grind 'em on a bench wheel, de-burr and re-gap. I use an adjustable gapping tool for consistency. They will fire easier off the sharp edges and stay cleaner - but won't last as long. I change plugs with oil changes and never worry:

 

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David,

I've never seen or heard of that technique before - interesting! Are you saying they fire like a platinum plug, but don't last as long? With as many miles as I put on my car (a few thousand maybe) they'd probably last years anyway!

John
 

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John, the reason most platinum plugs fire easier, is due to the smaller surface area at the tip. The more concentrated the area, the easier it is to fire, and firing at a confined point keeps that spot cleaner for the next firing. The problem with spot firing is wear. As you can see in the pic below, the area that wears is much smaller with a side-gap (or any other "spot-firing") plug than a standard one. So, in stock engines, they use platinum as the 'spot' to reduce the wear to give long plug life. A single platinum plug will have only one electrode with a platinum nib, and the other electrode in plain steel with much larger area for slow wear. Theose are the "50,000-mile" plugs. A double-platinum plug with have it on both parts, to sharpen the firing spot even more and still keep the low wear. Those are the "100,000-mile" plugs.

OK, so why not just use P-plugs? There are advantages to side-gap plugs and why they are used in racing, some aviation and other performance engines. Not only do they have easier sparking and maintain a cleaner spot, they also expose the spark to a more consistent open fuel-air mix than what goes through the traditional gap "slot", resulting is a better light-off, larger flame kernel, and faster, more complete burn of the charge. The more reliable and cleaner burn reduces fouling as well, adding to the reliability of ignition. Also, while you can change spark plug heat range, it doesn't help the issue of overheating of the side electrode. Hot electrodes are a common source of pre-ignition in HP engines (far more damaging than detonation) and the short side gap electrode is far less prone to overheating. Down-side: fast wear. Keep in-mind P-plugs are generally not recommended for very HP engines, as the 'spot' and other versions like fine-wire electrodes can easily become overheated and induce pre-ignition just like the old side electrodes.

So, although side-gap plugs have been around since the beginning of spark plugs, shrouded (full-cover) electrodes have been for stock engines for wear, and side-gaps for HP engines that see more maintenance. While there are now side-gap platinum plugs becoming available to get all the advantages, they are very pricey due to the large amount of platinum compared to a standard plug, and I can change plugs at every oil change and still not spend as much after 50,000+ miles than with the P-plugs. Down-side: not as sexy. ;) HTH

David

The yellow areas are sparking and wear points. With far more surface area, the shrouded plug will wear much slower and give longer life at the expense of advantages stated above:
 

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I change plugs way before they ever have a chance to wear out too.



I wanted to see if the animated GIF would work. All the platinum plugs I've looked at have that swedged or curved(whatever you call it) electrode. They also monkey with the end of the pin. Some are beveled like this one and some bevel the underside with a slanted back cut. I'm not sure how much difference all that makes.

Here is an Autolite platinum(photo said it was a platinum) that is doing some of that unshrouding of the pin. They cut it half way back.



Amazing the stuff I continue to learn on here. I never even contemplated what they were doing with the electrode and pin until now.
 

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I tried E3 plugs this year and so far no issues. I don't know about all that extra HP and fuel mileage they claim though.

Matt
 
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