Hi Folks, Just an interesting note. while waiting to hear from the insurance company about fix my ride I decided to do a few things. One of which was change the standard plugs to the #5 rapid fire. The increase in mpg is outstasnding. before the change my average mileage was 25.6 and after it was 28.8. thats just the plugs I ordered the new wires and cap but they haven't come yet. I wonder what they will do. Just thought this was interesting, Cheers, George(blueshark)[sm=yikesomg.gif][sm=bounceybounce.gif][sm=americanasmiley.gif]

 

Ive never heard that from rapid fires. makes me wonder how bad your plugs were before

 

I installed the Rapidfires in my 87 Vette and the increase in performance is noticeable. I agree they are better than the Champions.

mypetu39

 

When I took the old ones out they still loked good. I almost didn't change them. I couldn't believe the dif. I got the car from my cousin and he was pretty **** about maintenance. he really took great care of it. change the oil every 3 months even when it sat in the winter months. I've never seen a change like that from changing the plugs. the old ones were AC Delco 41-629 standars. I wonder if they were for iron heads instead of alum.

 

there is a noticable difference between iron head plugs and aluminum head plugs ( length of thread and the washer ) are dead give aways. If you changed them yourself you would notice the difference . I tryed to get a set for my 86 and the guy tryed to sell me the #1s no listing for my aluminum heads ,,,, good to know the #5s fit ty for the info

 

If your car has tapered seat plugs, you don't want to put the washer seat plugs in it. Could have compression leaks. My iron head 86 L98 has tapered seat plugs.[8D]

 

Mech 259, for the uninformed and the non-mechanic types, how can one tell if he/she has the iron head or the aluminum head????

mypetu39

 

easiest way is take a magnet and if its attracted to the head, then its iron.

84-early 86 had iron heads. they switched halfway through 86. all convertables in 86 had aluminum. everything else is aluminum.

 

Interesting insight on the AC plugs. But a question on the gas mileage: I live in Maryland, which is faily hilly. Not sure if that is the main cause, but my around town mileage is only 13.8! 92 stock LT1 with auto. I took one trip and the highway figures (at around 65 mph average) was a little less than 22 mpg. Do these figures seem about normal? Car is in good tune and I am not an aggressive driver(well, most of the time, he-he).