Spark plugs--AC 44 vs AC44s

My engine originally called for AC 44 plugs---Found some nos AC 44s . Whats the difference between a 44 and a 44s,and can I use them?

 

44S has a tip that extends maybe 1/16 inch deeper into the combustion than a normal 44. As long as you don't have any pop top pistons you should be good to go. The extended tips are supposed to stay cleaner, since the tip is hanging farther out into the fire in the combustion chamber. YMMV.

 

there 7/8 thread reach vs the 1/2 thread reach , the threads will stick out in the chamber besides the tip being farther out

 

NOPE--threads are same length


Found an old tune-up chart---correct plug for my engine was AC44,BUT said AC44s for light duty (whatever that is) So I'm good to go!

 

Be sure of the thread length. If enough of the threads of the plug extend further than the mating threads of the head into the combustion chamber, they can collect carbon and cause problems removing the spark plugs down the road.

 

Manufacturers specify a spark plug that puts the spark in the correct place in the combustion chamber. Take advantage of their engineering and use the proper spark plug.

 

Yeh,gaping at .035---some say to go more with pertronix,but no need to

 

only giving info from the manufactuer looked at the chart on the wall ..

 

better read it again

 

same chart on my wall

 

I have no idea why the chart has 2 "S designations,but as you can see,these plugs I have are not 7/8" thread----A lot of GM cars used these back in the day---they are not made anymore--notice Made in USA!!

Dogone it--I took some pics and can't seem to upload them *&^%^&never happened before,But anyway they have about 1/2" of threads and are the same reach as the Autolite 85's that I'm replacing

 

44S WILL exactly replace the 44 . As stated, the only difference is the extended tip. We used them in customer cars All thru the 60's, and no issues.

4TTRUK