head bolts

[shawnxj]

are the head bolts for the 99 4.0 the same as the 88 4.0? orielly's has them for the 99 but not the 88. i had to pull the head on my motor last year and reused the existing bolts but after i finish my stroker i'm gonna sell that motor so figured i'd be nice and put new bolts in before i do so. i'm gonna use arb's on the stroker but don't see the need for them on a stock motor

[5-90]

I think it's a matter of different heads, but same shanks. I've heard that the later screws use a 12-pt socket, but I haven't verified this.

[SilverXJ]

Yes, the later bolts are a 12 point 1/2" socket. As far as I know, all the 4.0L blocks use the same shank and thread for the head bolts. The 4.2L engine has 7/16" bolts.

[IH 392]

I find conflicting information, but I believe that only the '81 and later 258's have the 7/16" head bolts, I've only seen one that did, I know for a fact all of the '70's 258's have 1/2" bolts.

[5-90]

I find conflicting information, but I believe that only the '81 and later 258's have the 7/16" head bolts, I've only seen one that did, I know for a fact all of the '70's 258's have 1/2" bolts.

Now I'll have to go out and measure the screw holes in that 2685 head I have. But, I'm under the impression that the /early/ AMC six heads used 7/16"-14 UNC screws, and the /later/ engines used 1/2"-13 UNC. Could I have gotten that reversed?

[IH 392]

I say conflicting because I was under the impression that the last of the 258's had gone back to the 1/2" bolts????

I just went out and pulled a bolt out of my 1975 12cw crank donor engine and my caliper says it's 1/2" for sure!

Every 199, 232 and all but the one above mentioned 258 I've torn into have had 1/2" head bolts.
The V8's from 1967 to 1969 had 7/16" bolts and in 1970 they went to 1/2" bolts.

[amcinstaller]

ill check on the amc forums, but im pretty sure the older engines used the 1/2 inch bolts and the laters used the 7/16. thats why dowells had to be used with some for the 4.0 head swap, and part of the stupid plastic valve cover changeover. it IS possible however that they could have changed back to the 1/2 inch bolts though. ill check.

[bbarrett]

My 87 model had 1/2 inch bolts. I tore apart 3 258s during my stroker build, All had the 1/2 inch bolts. Only the one that came in my Jeep, is the only one im sure of the model.

[SilverXJ]

From what I can find the 71-80 uses 1/2" head bolts. Then in 81-88 they went to 7/16". On the 4.0L they went to 1/2". I don't think the 4.0L was ever 7/16"... 88 looks like it could be an in between year.

[amcinstaller]

yep, 1/2 inch till the end of 80, then 7/16 till about 86. then back to 1/2. 7/16 inch head can be spotted by that crap plastic valve cover, and apparently ruler straight passenger side on the head.