i have a 1974 with a 454. i don't have the car very long and do not have any details on the engine or work that may have been done on it in the past. the block is the correct numbers matching block, it has headers and an edelbrock performer and seems to have a slight cam. my problem is i purchased new plugs ac's r44t and they are totally different than what is installed. the plugs that are installed are ngk r gr4 v power that the tread is much longer with a washer, the r44t's are shorter with the tapered seat. does anyone have any ideas what i may have here or suggest a plug that works with this engine. any help would be appreciated.

That NGK plug is the wrong application. The AC plugs you bought are the correct ones.

Make sure the heads haven't been changed to an aftermarket design that uses a different plug.

Gunslinger2007-02-10 14:24:20

the ac plugs are shorter and won't even reach the treads in the head. how can i tell if the heads were changed?

Not to make it sound like you might be wrong...but are you sure it's a big block you have in your car? The small block takes a different configuration spark plug...it has a straight shoulder and a gasket.

i know a big block from a small block. what i don't know is what is going on with my heads. the plugs in them are straight bottoms with a washer and the tread is much longer than the r44t's. the r44t's won't even reach the tread in the heads.

Believe me, I didn't mean to be demeaning in any way. Something is very perplexing in the difference in plugs.

Maybe you have aftermarket heads...maybe you have Chevy heads, but they've been swapped from another application. I have no idea, but maybe truck heads used a different design? Just making a guess on that.

Get the casting numbers off the heads and someone here can ID them for their actual application.

do older big block heads use the longer flat shoulder plugs or do all big block heads have the short tapered shoulder plugs that i thought i needed??????????

I just looked it up...some truck big block heads use the spark plugs your car has. It looks like sometime in the past someone swapped out some truck heads on your car.

Looks like you will need the casting numbers off the heads to confirm that and what year application there are so you can make sure you get the correct heat range plugs.

Sounds like a good time to consider a set of nice aluminum heads for your car...maybe even fuel injection along with it...that would be schweet!

Like Gunslinger suggested, get the casting numbers off the heads and it will be easy to identify them. Your "block" casting number should 3999289 or 3963512.

thanks for the help. if they are truck heads are truck heads junk and why would someone use them. i will get the head casting numbers and post them.