Which Spark Plugs to use in a FE 406?
 

Hi guys

Can anyone tell me which are the best sparks plugs to use in my 406 to get the maximum performance. I am running a Holley 750 if that makes any difference. It is running a little on the rich side.

Thanks Paul

Paul,

It depends on your compression ratio. Any plug that will fit the older head physically will work, as long as you select the heat range for your compression.

If memory serves, most of them were 11:1. If yours is, then the Autolite BF32 (old number) will be fine. Have your parts house cross reference the number unless they have an old book. I'm sorry to say I don't know the new numbering system.

If your engine is a little fat (rich), you probably need to lean out the idle. Pretty simple with a Holley. Just close the idle screws (one on each side of the front metering block) back them each out one full turn and fire up the engine. work one side at a time. Adjust in or out and go for the highest rpm idle you can get with each screw. When you have done both sides, you can "play with it" to fine tune. May need a little more open on the curb idle. Make sure the curb idle screw on the throttle arm is not already too far open when you start setting the mixture.

With stock cam, compression etc. it should idle at 750rpm, with just a little hint of cam lope.

Hope this helps a little.

Al

Had to jog my memory on this one--no books to look at. The 406 uses the same plug as the 427 and other FE engines. The original number is BF32 on Autolites, but as Al said, I don't know what that cross references to today.

The original Champion number would be F11Y. If you want to go a little colder, you can use the F9Y.

I run Autolite 45's in my 427.

Compression is an issue to consider. Heat range etc. I'm running 11.7 to 1. alum heads. I run Autolite Racing series plugs. AR33. This is a replacement for the BF33. BF 33 plugs are worth alot of money now as a NOS plug. I've heard that Dove heads have been built over the years with 2 different size seat diameters (Hole size is what I'm trying to spit out) also some had tapered seats others had conventional seats. If you are running Ford heads, the AR 33 will work fine for starters. Any doubts, e-mail Geo Anderson @ Gessford Machine link on this site.

Hello Cobra 427 mnsi,
Well there's a lot of things to consider on plug choice.
#1 is availability. For the older type 18mm size plug, Your choices have been reduced from 20 years ago in the number of heatranges that you can get!!
Right now its either cold or hot, with no in between.
The old bf42s use to be good for a performance motor that ran on the street and had a tendency to load up the plug. This was a mid range heat range plug that offered a solution to extended street driving.
Now, this is no longer available. You have to run either a Autolite 45, which is really an old bf82, or the previously mentioned bf33s. The Bf33s come in either the standard version, or you can get them in the race plug. Their the same basic plug, but the race version has a cut back bridge for the electrode, and is a crome finish body instead of black. These 33s are really the old BF22s of 30 years ago. Same exact plug. So if you run them on the street they have a tendency to load up. They are a very cold plug.
So what is the gist of all of this.
I would run the Autolite 33s and keep my idle up around 1200 rpm in neutral. This helps the oiling of the lower end, ei. cam, lifters, piston skirts, and helps the intake track keep some velocity to keep the fuel suspended so the plugs wont load up. Its kindofa toss up these days. I remember that we used to run BF32s or 42s around the street for every day, and then put in a new set of 22s(the new 33s of today) when we would have a race to go to!!
This is also one way to handle the plug delema today. Run the 45s everday, and then the 33s when going to the track or whatever for more performance. Remember, a colder plug helps transfer more spark charge because the heat doesn't elevate the resistence in the electrode.
I hope this helps!!
Tom Lucas FE Specialties 916-339-0427

The AR33 racing plug style elctrode is a good place to start if you plan to introduce NOS, heaven forbid! Yes it is a cold plug, but you want to start cold and progress towards hot to the optimum. Street plugs and fresh race plugs at the track are probably the way to go for most types of drivers. FE plugs are easy to remove and I don't mind the expense of changing plugs, just don't want to find signs of the plugs taking aluminum, hot plugs/hot engine bay/ less than optimum timing,not enough octane and you got pre-ignition. As loud as these Cobras are you won' hear the pinging and might not feel it. Plan on progressing and experimenting cautiously until you have it all jetted and dialed in.