258 Head Specifics

[swatson454]

The search function wasn't my friend so I must ask. Can someone point me to the flow specs, intake runner volume and chamber volume for a 258 head? Are there better or worse casting numbers that I can be on the lookout for? I'm just doing a mild, budget build but I could really use those numbers to help me get the cam sorted out.

Thanks in advance.


Shawn

[Cheromaniac]

The 258 head is only useful as a boat anchor. The 4.0 head is light years ahead and it'll be even better if you port it.

[amcinstaller]

yep, hes right. and unless you have the mani's that go with it, youre kinda stuck finding those too

[IH 392]

I believe that with the proper porting and big valves the 258 heads can be made to flow as much or even more than the 4.0 heads, and with the OEM intake and exhaust manifolds yet!

[Cheromaniac]

I believe that with the proper porting and big valves the 258 heads can be made to flow as much or even more than the 4.0 heads

It'll take a hell of a lot of work and you'd probably still end up with a polished turd. You'd do much better to buy a '91-'99 4.0 head, port that instead, and keep the stock valves. The 4.0 head is designed to induce more swirl than the 258 head and has dual quench pads, so detonation is less likely with the 4.0 head despite having a 7cc smaller chamber (0.7:1 higher CR).

[amcinstaller]

maybe bigger power with that intake and exhaust but not with the american ones. interesting though, never seen a VAM set of manis before.

[johnj92131]

I believe that with the proper porting and big valves the 258 heads can be made to flow as much or even more than the 4.0 heads, and with the OEM intake and exhaust manifolds yet!

You may want to look at "the collective works of Nosigma" for accurate flow data on the different AMC/Jeep heads. May surprise you.

[swatson454]

Thanks for the replys, guys. My deal is that I don't want to get into modifying brackets and fooling around with the intake to make it fit a 4.0 head and I already have a header for a 258. Who knows, maybe if I can find a smokin deal on a 7120...

I browsed through some of Nosigma's stuff. Maybe I need to look harder.


Shawn