87 mighty max blackened plugs

[madman23420]

i just got an 87 mighty max with a few problems. i replaced the spark plugs and drove it maybe 2 miles and it started missing so i rebuilt the carb cleaned the already blackened plugs and again ran it about 2 miles and the plugs started missing again. when i pulled the plugs they are smut black.i think i may have an intake valve leaking do u think this could be the problem?i dont think there is anything wrong with the carb. i recently pulled the head on this truck thinking i had a leaking valve in the combustion chamber ther is a hole beside the spark plug hole for each cylinder i guess it it for a diesel conversion or something but only ony of the holes is open and it leads through the intake to the carb the other holes are plugged somehow. but the no 2 cylinder is letting it blow exaust back in the intake and killing my combustion how can i plug this hole and what is it for

[madman23420]

its a friekin jet valve. or it used to be atleast. someone tried to do away with them but didnt do a good job now its leaking on the no 2 cylinder they sell an elimination kit but some other crap is jammed in the holes im going to drill tap and plug the holes from the bottom then see what happens maybe this will help someone else if they have a similar problem