3 litre Plug Gap

[TheVancen]

I've searched a bit looking for the optimal plug gap for the Gen one three litre but I've come up empty on that front. Car is a pretty stock 1991 MTX and I'm going to use Autolite Coppers.

 

[Off Road SHO]

If I remember correctly, it's something like .044". And for the most part are already gapped that way. At least the MotorCraft and Autolites were.

Tom

 

[TheVancen]

If I remember correctly, it's something like .044". And for the most part are already gapped that way. At least the MotorCraft and Autolites were.

Tom

Thank you. Just wanted to be sure.

 

[sperold]

These motors work best with the exotic metal spark plugs and Ford's Motorcraft plugs are a good price and available. It has something to do with a "wasted spark" ignition system where 2 plugs fire at once while only one does the work. The theory is one time the plug spark jumps from the center to the side bar and the "wasted spark" plug situation is the opposite.
The back row is fairly hard to change. So it is good to have plugs that will last a long time.

 

[Off Road SHO]

Sperold,

You are close. While two plugs do fire at once, one center electrode to ground and the other ground to center electrode, the spark that is wasted is whichever one is firing on the exhaust stroke instead of the compression stroke. If it doesn't fire on compressed air and gas, it is wasted.

Tom

 

[TheVancen]

These motors work best with the exotic metal spark plugs and Ford's Motorcraft plugs are a good price and available. It has something to do with a "wasted spark" ignition system where 2 plugs fire at once while only one does the work. The theory is one time the plug spark jumps from the center to the side bar and the "wasted spark" plug situation is the opposite.
The back row is fairly hard to change. So it is good to have plugs that will last a long time.

I've heard that these engines also don't like the E3 plugs either. Is there any truth to that?

 

[SHOdded]

Stay far, far, far away from these "gimmicky" plugs: splitfire, E3, even the +4's.

 

[cali+Mocasho+]

I've searched a bit looking for the optimal plug gap for the Gen one three litre but I've come up empty on that front. Car is a pretty stock 1991 MTX and I'm going to use Autolite Coppers.

why copper? i believe stock is double platinum motos

 

[cali+Mocasho+]

i put ngk laser iridium plugs with .44 gap and dont have a problem.

 

[SHOdded]

Copper is the best conductor, but gets used up quickly. Platinum & Iridium are good conductors, and last a long time.

----------------------Copper----------Platinum--------Iridium
%IACS--------------100.0------------16.28--------------32.60
Siemens/meter--5.800E+07-----0.9442E+07------1.891E+07

Siemens/meter being the unit defined for electrical conductivity.

 

[AREA 91]

.042 - .046 is the gap stock gap range.
Motorcraft AGSP32FM
Autolite APP3924

 

[itwonder]

You can still get the exact spark plugs the SHO was delivered with from the factory NOS: Motorcraft AGSP32PP from Green Sales Company. Well priced, and nice folks to deal with.