Spark Plugs

[Clunker]

In my infinite wisdom, I decided to try some expensive iridium NGK spark plugs when I upgraded the ignition to a Pertronix II and Flamethrower coil. I figured that with the added performance of an electronic ignition, I would not need to use some outdated, low-performance spark plug. I pulled a couple plugs today and found them to be completely carbon-fouled except for the tiniest spark point. Many people on this forum suggest using the original Autolite/Motorcraft copper core plugs. Do any of you think this is still a good choice with the electronic ignition? Anyone have better luck with something more modern?

[brkdncr]

can't speak from experience, but if you're changing plugs on the recommended schedule stay with copper. If you're going 50k plus go to better plugs....

[mouse]

I have tried a bunch of plugs on my 390 fe and like how the ngk AP8FS run best so far, may try a warmer one next when they burn out. for these ngks it is AP7FS AP8FS AP9FS warm to cold ranges, these are the copper plugs. I am running a msd 6a box on a duraspark distributor with a blaster ss coil. being as I have a cd ignition, iridium plugs would just not last long.

[idaho_cowboy]

I used to blow through plugs of all kinds. I finally settled on 45 Autolite's, and havn't had an issue since. They are a good plug and just seem to "agree" with the FE.

- Joseph

[sargentrs]

Autolite or Champion 45's have always been my plug of choice for older vehicles.

[MadMike]

In my infinite wisdom, I decided to try some expensive iridium NGK spark plugs when I upgraded the ignition to a Pertronix II and Flamethrower coil. I figured that with the added performance of an electronic ignition, I would not need to use some outdated, low-performance spark plug. ...

After installing the Pertronix and plugs, did you retune the carb for the new hotter spark?
Did you remove/bypass the coil resistor wire and have proper full battery voltage(12+ Volts) to the coil? If not you are not using the full potential of both the pertronix system and the iridium plugs. Are you sure the carbon buildup is not residue from burning off buildup off the pistons/chamber?

Nothing wrong with coppers but they do lack durability. If you have ditched the points, you are probably wanting to enjoy driving your truck rather than tuning it every 3-5kmiles. Iridium's will help in extending periods of tune.

Do any of you think this is still a good choice with the electronic ignition? Anyone have better luck with something more modern?

Ditching the points for the Pertronix system is a step in the right direction. Points are a point of failure, wear and can be a PITA to set up correctly. For a driver/cruiser/work truck the only other upgrade I would look into would be a Duraspark igntion system. Pertronix offers the simplicity of the electronic pickup without the complexity or 'ugliness' of the added Duraspark components. MSD box is not necessary unless you plan on revving or racing the engine quite a bit. But for a daily/work truck it will just add complexity and another failure point. The Pertronix is perfectly simple and pretty durable.

I prefer the Denso TT Iridium plugs. Denso were the first to do Iridium and the TT plugs, with the twin micro points allows for a smaller gap while allowing more of the spark to be exposed compared to conventional spark plugs. Main advantage of iridium is the wear characteristic, it can keep a finer, sharper point for the spark to jump. This was part of the advantage of platinum plugs, the electrode would last longer maintaining the correct gap compared to CU plugs. With the Denso TT smaller points require less power saturation before the spark needs to jump, saving power and stress on the coil. More usable power in the spark for a complete burn.

[Ranchero50]

Points are fine, it's the condenser that craps out. I never saw any wear issues with basic plugs. High mileage plugs are great for ***** access on newer cars. Old trucks with low comp engines aren't gong to see a huge benefit. I'd run the hottest plug the truck will stand as the low compression weak rings will allow some oil in the chambers. Sounds like that's what happened to the OP.

In all honesty, unless you have the compression to blow the spark out you really don't 'need' a hotter ignition. On both my boosted cars I hit that limit and it's either tighten the gap and get a stronger spark going.

[Clunker]

There are several factors involved that could be related to the fouled spark plugs. First, I have had a leaking brake booster, probably since I bought the truck. My brake fluid level kept dropping, but I never found any leaks. I think that the engine has been sucking in brake fluid through a failed seal. You can hear it slightly when you press the brake pedal. I can't imagine that this helps produce clean combustion.

I did adjust the carburetor after installing new plugs, wires, Pertronix, and Flame Thrower. Admittedly, carbs are not my strong suit, but this Holley doesn't seem to have any adjustments other than idle mixture, idle speed, and choke. I tuned mixture and speed until I reached maximum vacuum, but it has always smelled like it is running a little rich. The PO replaced the resistor wire with a regular wire, but I still didn't trust it, so I ran one straight from the ignition switch (full 12V).

Plugs are a cheap investment, so Maybe I'll give the Autolites a shot.