Ok......im not much of an AMC guru but when i bought a 76' cj-7 it had a t-18 with a 304 thats was supposed to be "radical" as the P.O. had stated.....not! The heads were junk, the bottom end had .040 bearings when it was stock size which grooved the crank so bad it had to be taken to .020 . The oil pump housing was so bad i had to buy another one which i got from Bulltear . The dist gears were toast and not to mention it had a Summit cam with 3 less lobes than it should I know its crazy isn't it? haha But ne ways he gave me another set of heads that he for some reason he had lying around but i took em to the local machine shop and had em tore down to verify if they were good or not so they came back A ok and i installed new Crane valve springs and seals but i have them installed on my motor and as i just finished painting it i noticed that just the two inner exhaust ports have 3/8 threads and the outer two have what looks like 1/4 threads????? The other set of heads had 3/8 all the way around so i never thought twice to check. Number 3, 5, 4, 6 have 3/8 threads but 1, 2, 7, 8 have smaller......Why?!?! Can somebody explain if and why they are like that? Are these special heads or shitty?