258 head fitment

[Elbogrease]

Hey Guys,
Does anyone know if a 1985 AMC 258 i6 / 4.2l l6 head fit a 1974 AMC 258 i6 / 4.2l block? I was told it will only fit back to 1978.

 

[IOPort51]

the only thing that comes to mind is that the head bolts are different sizes, diameter. but I am not sure how that would mess with this.

 

[Loadnplenty]

I have a 90's model AMC 258 i6 / 4.2l head on mine and it works well.

 

[Elbogrease]

I went online and noticed gaskets for the 85 head only works for 83-87. I would what has changed.

 

[BlackOmega]

I went online and noticed gaskets for the 85 head only works for 83-87. I would what has changed.

It's head bolt diameter.

If what I read about the Cj's is accurate, somewhere between 83 and 84 they went from a 1/2" bolt to a 7/16" bolt.

It seems that the 1/2" version is more common. I had a helluva time finding bolts for the one I'm working on. it has the 7/16" bolts.

Note: In '84 there was a hardening issue with the head bolts. It doesn't affect all of the '84's. There's a serial number range. Although, I'd just replace them with some ARP bolts and not run the risk of breaking a head bolt off in the block.

 

[Elbogrease]

Good to know. Thanks

I'll have the head drilled out to 1/2". Definitely will go with new bolts.