A little guts trying to see if it clears the piston, you can pick up 8 autolites for $12, instead of risking that chance. Free things break expensive things you know.

 

i highly doubt the stock plugs just barely clear the pistons, considering you can upgrade cam lift over .150" while comfortably clearing the pistons. i thought about that and decided, the worst that will happen is that the piston will hit the ground strap and bend it and possibly put a tiny knick in the piston. plus my buddy ran the same plugs in his 86, i was just making sure theyd be fine. it wasnt like i threw in a z cam and decided to try firing it up.

 

uhm yeah 86 and 89 use different plugs anyway. there is a reason they are the lenght that they are. you are asking for trouble if you ask me, not to mention once the threads get covered with carbon and soot, they will be a bitch to get out. and how much more the valves can open compared to stock has nothing to do with how close the plugs are to the pistons.

 

just for the record the thread lenth is the same, its after the threads that it gets longer. explain to me how vavle lift is irrelivant to plug clearence.