I have a 68 dodge dart but my engine came out of a 74 duster(suposedly 225).. now the other day I bought 6 NGK v-power plugs for the 74 engine. I took out an old plug and tried to install a new one, but the ratchet just spun..so i tool it back out to look at it in comparison to the old(champion)one..... they are two difrent lengths >.<; even the lengths of where the treads are was different (old one was much longer)..I cheked with ngk's site and said the ones i have are right for 225 3.7L duster 74....so is my engine size wrong or is it difrents in brands or what?

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I like the cars that go VROOOOOM

not the new ones that go wrrrrr -.-;

Did someone change the head to a later one which takes the smaller diameter spark plugs?

-shrug- I'm not sure... the guy I bought it from did't mention that.. it had elec. distributer, but i put my stock 68 one in with no problem. wating to buy orange box..

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I like the cars that go VROOOOOM

not the new ones that go wrrrrr -.-;

Try putting the plugs in the original 68 head. The size difference between the early and late plugs is fairly obvious.

What does your head look like? Does it have the "drool tube" style spark plug holes or the small holes like a V-8?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2