Technical Modern Spark plugs Iridium Ford V8 Flathead

Im running a electronic E-Fire Distributor plus MSD 6AL with Stinger 60,000 volt coil on my 39 Ford V8 engine.... i would like to add a modern spark plug to this system..... i realise i may need to make mods to heads or a adapter to a different style of Iridium spark plug..... Can anyone point me in the right direction or tell me what i can use?...


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To what end? They are designed for long miles between service but that’s all isn’t it? (And expensive)

 

The high power ignition system it now has is a bit hard on standard plugs & Iridium gives a better spark....


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Not sure I'd say they give a better spark. They demand slightly less energy to make a spark (good for the high rpm high compression situations with a slightly too weak ignition system), but with those ignition components it sounds as you should have plenty of that. But sure, I can see those sparks eating your stock plugs quicker than you may like, iridium should help that.
No idea what kind of plugs fit your heads though.

 

What brand and number are you running now? It will be easier to figure out what you need with more info. What heads are you using?

 

Here I go again comparing apples to oranges. You may see some benefit, or not.
I've worked in the auto parts business since 1993 and in new car dealership parts departments since 2000.
I've worked in Mopar stores since 2007. Numerous times I've seen customers buy into the "supper plug" manufactures marketing. They'd install the latest greatest spark plugs and then end up at the dealership service department with issues. Usually these issues would be fixed with the installation of the OE copper spark plugs.

Reading your first post it sounds like you're running a flathead. If so, you may be at the point of ignition overkill now. Is this a pressurized Henry V8? If so maybe you do need the best plug out there, or is it just bragging rights? Anyway it could be fun to play with the plugs. Possibly a drag test shoot out, so to speak. Back to back quarter mile runs then compare the results each plug change did, or didn't, provide. Anyway, try some different plugs and report back to us.

And if it is like Torana68 states above and you are just looking for longer plug life, then congratulations for soaking up so many miles regularly in a hot rod that plug life is now an issue.
-Dave

 

Hi Dave its a 39 flathead with H10c champion plug....not after any bragging rights just want a long life plug that wont erode away so soon & yes its a daily driver...


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H10c champion in 39 flathead... thanks


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It has Champion H10c plugs..... will probably have to machine a adapter to make a suitable plug work were my thoughts?


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My experience with spark plugs is that Champion plugs don't last very long, I would try some other brands without going to the extreme measures of going to iridium! Try NGK or Bosch, they both work good for me.

 

Unless you're driving your car over 20K a year, any plugs (even Champions) should last a long time. If I were experiencing shortened plug life, I would first look into my state of tune.

As an aside, several years ago, out of idle curiosity, I looked for Iridium replacement plugs for a flathead and couldn't find any. All available had quite a long reach for aluminum heads. I see no reason why any of the plug manufacturers would tool up for a 3/8" reach application. If you think you are experiencing problems now, just wait until you try to "jerry-rig" something not intended for this specific use.

 

I only use Iridium only if they are a B I tich to get to.

 

Champions are the plugs where most boxes say made in US.

 

I bought a set of 7/16" reach extended tip Champions for the Edmunds heads on my car off eBay. When I got them, the boxes said "Made in France".

 

I ran Champions for years, then noticed the quality go down hill. Never had any luck with Autolite plugs ether. I have switched to NGK in everything and haven’t looked back.


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The last time I used Champion plugs was when I built the engine for the car in my avatar. They were misfiring within two weeks and I tossed them. (Your experience may differ) I had trouble with Champions in the past but they offered the specific heat range for the engine I built. I'm not likely to ever use Champions again.

I now run Autolite copper plugs and get at least 2 years service out of a set. The last flathead I put plugs in I used either AC Delco or NGK, I don't remember which but I wanted resistor plugs because I was installing a set of new electronic gauges and didn't want any RFI "noise".

I'm also very unlikely to use iridium, or even platinum spark plugs because I don't see an upside to it, but everything I own I only drive on the street so I don't really have a need for the type of ignition system you're (nyall) using.

 

I may be mistaken in my thinking but I’ve been working with the understanding that the iridium plugs were meant for aluminum heads as many modern vehicles now have..

 

I would be less concerned with modern plugs,and more concerned that the plug tip goes through the head all the way.Some plug/ head combinations leave a couple turns of thread unused which results in a tip that's shrouded.Guys will re-leave the area around the plug tip so theres a good flame travel to the chamber.

 

sunbeam>>>Champions are the plugs where most boxes say made in US.>>>

The cardboard box maybe. But what about the plugs? Jack E/NJ

 

I have the opposite problem with Edlbrock heads and extra valve lift. I have to use a shim so my plug tips don't hit and close the gap. That's will a standard tip, the irridiums I've seen are projected nose, maybe not all.

 

As others have mentioned, it seems all the iridium plugs have too long a reach. I did a quick check and found no cross reference for my NGK B6-L plugs for either, Denso or Bosch. If you are running Champion I would first switch to NGK and see if there is any difference.

 

Nyall, as far as I know there are only 2 choices of reach in iridium plugs right now both about 25-26 mm or so. The h10c is 11mm reach. If you've got your heart set on iridium plugs the only thing I could see doing would be to have some spacers machined up.

 

Yes my thoughts exactly..... the only thing is i need one in the right heat range & one with 1mm projection....


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This might do it.

 

Yep! That's it guys; don't worry about getting the carb set right or even stopping some of the minor leaks. The ignition is close enough the way it is. Let's get some of them new Iridium sparking plugs like are in my Mom's new Lexus and that'll solve all the problems we're havin' with this old flathead!

Oh shit! it won't start? Dayum, the pistons closed up the gap because the plugs are 1/8" too long! That's OK, we'll get uncle Joe to machine us up a set of spacers . That'll cure that. That's Hot Roddin'!

 

Tubman, thats some funny shit there. Believe me I've seen plenty of that. Basics first.

 

It runs perfect it starts first pop it idles smooth it doesn’t overheat & cruises at 100kph no probs..... like i said i would like a longer life spark plug....Cheers...


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Great i will check that out.... Thank you


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"Nyall" - I guess I should apologize for my previous post, but it was primarily done in humor. It seems that you have done your homework but have come up against the weakest link in the ignition system. I had a similar problem with a flathead I built for my '36 about 25 years ago. On that engine, I installed an MSD "Ready to Run" distributor with the matching control box and coil. My problem wasn't with spark plugs, but with the cap. The spark was so hot that it would eat through the coil tower on the distributor cap in a couple of weeks. The first time it happened, I bought a new cap from MSD ($$$) and cleaned everything up and made sure the wires were well separated. After a few more weeks, I had the same problem. Luckily, I found out that standard GM caps fit the distributor so I didn't go broke. Ever since then, I have used Mallory "flattops" on my builds. I figure I'd rather look cool than get the last 2% from the ignition system.

The 1/2" reach Iridium plugs mentioned above were not available when I looked, which admittedly was several years ago. They should work with a proper spacer (or maybe a couple of extra washers).

My only other suggestion is that if it starts to run sour down the road, check the distributor cap.

 

Thanks for that.... & yes you’re right the cap will now be the weak point..., its a 2bolt crab type dizzy..., if i had problems i was going to try the $$$$MSD cap which i thought was the only other cap that would fit...Does a GM cap fit? If so do you have a part number i can go by? Thanks.....,


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