Hello,

Can anyone please tell me what the spark plug gap for a 351M engine is?


Thank You

 

With the factory Duraspark ignition, .042 - .046

 

hi sorry to buzz in. what do you think the gap should be when running an MSD system?
thanks
jim

 

This truck has the factory ignition spark set-up. So, sounds like .042 - .046 will work?

 

Hey OrangeJuice,
My 78 400 is set at .44 i belive i read that in some manuel

 

Yes, somewhere in that range. I generally gap mine at .044.

As far as aftermarket ignitions (Mallory, MSD, Crane, Jacobs, etc.), some recommend opening up the gap due to more electrical current being available with their system. You'd just need to play with the gap based on the recommendations of the respective manufacturers.

 

I believe 42-46 is correct, there should be a sticker on the radiator support and/or valve
cover that should specify.

 

I run 8.5 mm wires and premium cap and rotor and have my plugs gaped at .60 the truck runs great with smooth idle and great performance.

The TFI coil is the difference, I could have bought a Blaster oil filled coil but the TFI Ford coil does a better job and you can pick one up at the auto wreckers for cheap, also make sure you remove the resistor form the ignition wiring it has one, the one that goes to the coil.

Rick.

 

so you think going from .44 to .50ish might lean it out a bit?

 

Because it is multiple Spark Discharge(MSD) with the wider gap and longer spark jump time I believe the air fuel mixture will burn more completely or less raw fuel unburned.

You still require a good coil to give a great spark in order for this to work.


Rick.

 

Should be .10 more so aroun .50 to .54

 

I'm running a Mallory Dist, Accel Cap/rotor, and MSD 8.5 wires...
What should my gap be?

Also what is the 351m speck for spark plug torque?

Thanks!

 

7-15ft.lbs.for 14mm and 15-20ft.lbs. for 18mm plugs.

 

Thank you! Time for a new torque wrench...