Spark plug

[SBSerpent]

What is the recommended spark plug for a stroked 351W Ford Racing Motor (392 CID)? This is the 'stock' motor that came with my 2011 BDR #983 build.

[eschaider]

What does the engine builder say to run?

Ed

[Tommy]

No guarantee these are right for your engine, but the 408 Windsor I used to have used Autolite AR 3932. They were a little on the cool side and tended to foul when not run hard.

[bobcowan]

I always used a standard Autolite 3924 copper core plug. They're easy to find, inexpensive, and work well in all conditions.

You have to change them about every 25-30K miles. But for most Cobra's that's every 5-6 years or so.

You can spend a lot more money on iridium and platinum. All that does is extend service life. And some ignition systems don't do well with those types of plugs.

[spdbrake]

I agree on the Autolite 3924 like Bob. Also the Autolite AR3924 (cutback strap) are great. I've had a my best readings with NGK BKR6E (6962) v-power plugs.
But I admit that's after I had tuned the carb using an AFR gauge.

[Moritz55]

I have a Roush 351W stroked/bored to a 427cu and MSD 6AL , 510HP.
Roush recommends for my engine Autolite AR3923, heat range 3 (one heat range cooler that 3924) .. however I have better luck using NGK's so I use the equivalent NGK BKR6E-11, heat range 6 (stock #2756) just as "spbrake" recommends.

I also gap my plugs to ~0.045" because of the MSD 6AL.