Spark Plug Manufacturer and Gap

[Philip Messer]

I pulled all eight spark plugs in my 351 stroked Windsor (392 CI) without scratching a fender or valve cover! (Pretty good for a guy with ten thumbs!) The plugs were a nice coco brown color with gaps ranging form 33 to 40 thou. (First time I had pulled all of the plugs.) I remember reading past Club Cobra threads that concluded the best overall gap was 45 thou. I purchased a new set of like-kind replacement spark plugs (Motorcraft AGSF 32 C), set them at 45 thou and WOW what a difference when I got back on the road!!

OK, I am sold on the 45 thou. gap setting, but what about the spark plug itself? Is Motorcraft the best spark plug for the street? I discovered that NGK and Champion make the same spark plug (as do most likely others). Anyone found any of these spark plugs better/worse than others? And what about the heat range? For street use, should we be using cooler or hotter plugs? Or is the original spark plug that came with the crate engine the best to use?

Phil form Phoenix

[wtm442]

I use Bosch Platinum plugs FR8DPX in my 351W. IMHO, I think most all plugs are the same when new. But what are they like at high mileage? There is the difference.

But with good plugs around $3 each, just put in a new set every spring. That's what I do.

[Bob In Ct]

What are you guys torqueing to with aluminum heads?

Bob

[Philip Messer]

The proper torque for spark plugs in an aluminum head 351 Ford Windsor is 7.2to 14.5 ft-lbs. I have been torquing at 14 ft-lbs with anti-seize lube on plug threads and the engine cold.

[Ron61]

I have the best luck using Autolites in both my Big Block and the Stroker. I run a Jacobs Ignition and it will not work with the platinum plugs. It measures the resistance of each wire and plug gap and the Platinum plugs throw off the measurements and make it run lousy. I use about 2 sets of plugs a year.

Ron

[Philip Messer]

Ron,

Interesting that you exclusively use Autolite plugs. Back in the 60's and 70's, Autolite was the plug of choice for 396 and 427 Chevy engines in my race world. The higher the performance, the cooler the plug. I would run cooler and cooler plugs until they started loading up and then I would step up a heat notch. Not real scientific, but effective!

Phil

[Ron61]

Philip,

Sounds as if you and I both used the same scientific method of determining plugs. My Big Block won't run worth a darn on Champion, but the Autolites work just great. Took me two days to figure out what was wrong a few years back when I decided to try a set of Champions. Both engines run great on the Autolites and I just stayed with them.

Ron