[updated:LAST EDITED ON 20-Oct-02 AT 02:53 AM (EST)]I drive one of these Ford four-banger Rangers for work sometimes, so I thought I'd check out the forum here.

I've owned a Nissan car that had the same design, and I've heard of others.

I guess my input would only be that beyond centering a sparkplug on/in a cylinder, is there ever a correct way to do one spark plug? I guess that depending on the intake valves and the combustion chamber design, spark plugs could be offset a little bit for optimum results, but I have to wonder if the amount of engines with spark plugs coming in from the side of the heads really wouldn't benefit from a second spark plug for each cylinder?

To me, at least, the only nearly 'correct' design of a single spark plug is a Hemi-head. Toyota, Honda, and Chrysler have used them, as others probably have, but it's still a rare occurance.

I'm guessing that standard lower-cammed, and SOHC, engines have heads that don't allow the centering of a single spark plug in the Hemi-style very easily, so that's why we see the dual spak plugs on those engines. I haven't looked, but I would bet a lot of the 4-cylinder centered single spark plug designs are dual overhead cams these days.

Hmm, now that I think about it, Honda made, or makes, single cylinder four stroke motorcycle engines with two spark plugs. Given their reputation for making motorcycle engines (or any engines for that matter), I'd say they probably think they're doing something beneficial as opposed to trying to get around a bad head design.

Not sure what I'm getting at here, but I like the idea of two spark plugs per cylinder

I've got to say that this little Ford (is it a Mazda engine?) Ranger is running better (with more miles on it, too) than all of the S-10's we have that have over 100k miles. (Holy-geez S-10 four cylinders and transmissions are crap...)

Best,