6x-8 heads
 

hi guys, just got back from the machine shop. had my heads cleaned and magged. no cracks, I was looking them over and chasing some threads when I ran across this one above the crossover on the driver side. its 5/16 and not very straight. doesn't look to be a helicoil but maybe it is. do you,all think its ok or should I do something about it? not that great of a picture but you get the idea. its a little straighter than it looks, but not right. it threads in 1/2 inch. thanks BLUE TA

Those holes are 3/8"-16, not 5/16". Not sure what you're asking about. Can't see pic very well.

thanks for replying gto freek, yes, I understand that the holes are 3/8 when I found this 5/16 hole by the crossover I was puzzled why someone would do that. I can screw a 5/16 bolt in the hole and its tight. but not perfectly straight. im wondering if I should leave it alone. or change back to 3/8. it must have been damaged at some point but I don't understand how it ended up 5/16 but it is. would the 5/16 bolt clamp enough at that point? thanks BLUE TA

Does it have a thread insert in it or something? Trying to understand how it got down to 5/16" from 3/8". I think I would try to change it back to 3/8" if it won't mangle things. Also, being crooked isn't good. It won't clamp as well, and the 5/16" will only torque to 20 ft. lbs., instead of 35.

You can put it the passenger side rear and it won't matter.

thanks for the replys, gto freek, yes it does look like there is a threaded insert in it. but they did a really bad job. not only the wrong size but not straight also. I guess I should do some measuring and see if its in the right location. and not off center. I could switch head location left to right but would it seal back there also? thanks for the help, BLUE TA

hi, I did some measuring and the center of the hole is off. from the front of the head its 1/16 short and from the deck its correct. maybe the insert was done so bad I might be stuck with the 5/16 bolt. I wonder if it will seal in the back if I switch them side to side. thanks for any insight. BLUE TA

This.

If you do this then that questionable bolt hole isn't used at all, it's not used to seal the intake when it's situated back there.

Only the '64 and earlier intakes that use 12 bolts need the rearmost intake manifold bolts to seal the intake to the head. The '65 and later style intakes only use 10 bolts, the intake doesn't seal the full length of the head like on earlier heads.

thanks b man and 54 nomore, that solves my problem. I knew with all the knowledge here you all would solve this issue. I didn't see it till I got them home from the machine shop. now to a little bowel work. thanks again, BLUE TA