Spark Plugs for th 455

phil swanson

New member
Jan 7, 1998
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Hello again,

I was wondering what the consensus of spark plug types is. I have
a 455, 1973 model w/o HEI. I went to my local Pep Boys and bought a set
of AP86 Autolite Platinum's because I have had good luck with them on
other cars, all Fords. The book called out AP 86 plugs for the same year
Tornado, so I got a set. What a disaster!! I ended up with major
dieseling. I could have driven the thing to Vegas from San Diego on the
after run. I sent away for Dr. Olds book, aka. Mondello Enterprises out
of L.A. He is strong on NGK plus and recommends the XR-5 which is way
different in heat range from the Autolite 86 like in the Autolite book.
In fact the NGK is equivalent to the Autolite 73 to 75 according to
Mondello. I bought a set of the NGK plugs today and I am going to see if
I have stopped the dieseling. I was just wondering what you all ran. I
am a little leery of the fact that the NGK is not platinum but if they
run good, I guess I don't mind changing them more often. Has anyone done
any tests on the motorhomes to find the best plug? Any information
would be helpful to alot of us, I'm sure.

Thanks, Phil
Swanson