258 Performance Gurus Please Advise

[JAG811]

Ok .... here's the dealio ...

1 - I'm in Australia. 2 - I'm looking at buying parts new, not junk yard finds, cause I'm in Australia. Junk yards are full of Holdens, not Jeeps.

I'm rebuilding my 78 CJ7 . I'd looked at a 2 stage rebuild. 1-Rebuild the vehicle. 2-Engine swap injected Chevy V6 from Novak.

Then I started looking into fuel injection kits. TBI looking great at the price compared to MPI. Then I realised with a 78, TBI (Howell) is the only option I have - Problem solved. Looking like a HEI dissy upgrade to match.

Then I looked for a factory sized head that was converted for unleaded fuel (stainless valve seats) but couldn't find anything, and managed to find the 4.0L head swap mod.
Throw in a new manifold and exhaust and a few more mods to make it work, and I'm looking at the price of an injected Chevy V6 anyway getting some fantastic fuel economy ????

I like the idea of keeping the AMC 258 i6 / 4.2l , with the Howell injection for something around $1500 with a dissy ..... but it seems a lot more complicated then that ... if the bottom end is bigger due to bottom end rebuild it looks like there may be some problems with the Howell system mapped to stock AMC 258 i6 / 4.2l .

Need help from a AMC 258 i6 / 4.2l guru ..... what's every one's take ??? Major mods (4.0L head conversion) scare me, as I tend to lean towards the bolt on options and don't mind paying for them. Where to from here ???

(Please excuse me if minor details are wrong)

 

[Sasquach]

Well since no "performance Guru's" are stepping up I will give you an "average Joe's" view, I went with a 4.0 head, Mopar MPI and a cherokee tube header. Those mods made a big diference and am perfectly happy with the results, the Mopar system is not cheap as you are aware but for what you get in the kit(very complete) I do not think it is overpriced by any means. I would do it over exactly the same again.
The Mopar system is compatible with your 78, they initially published they were not but that was only due to CARB certification in Ca. That has been cleared up now(or I'm in deep )

 

[JAG811]

Thanks Sasquach.
I'm starting to take to the idea.
I've been reading all of the 4.0L head info I can to find out what's involved.
So as one average Joe to another. Regardless of post dyno readouts and how much improvement it makes, ect,
1 - Is it as simple as bolt on bolt off ?
2 - A 4.0L head must be unleaded compatible?
3 - I think I found somewhere (could even be thread below somewhere), where they named exactly what years to chase for the best performance .. But what about the intake manifold ? Will the 78 match or do I also need the 4.0L intake manifold ?
Thanks again for the insight !

 

[Cheepjeep85]

I can't remember the exact years or casting numbers for the 4.0 head but seems like 1992 and up is what you want, the 4.0 head is unleaded compatible like every other american made car since the late 70s, and. The mopar kit will come with a new mpfi intake manifold, but you will need a new 4.0l header for the exhaust.
Do a google search for alabama cylinder heads, they cast new 4.0 heads but they are pricey. I would give you a link but can't right now.
Sent from my DROID2 using Tapatalk

 

[JAG811]

I can't remember the exact years or casting numbers for the 4.0 head but seems like 1992 and up is what you want, the 4.0 head is unleaded compatible like every other american made car since the late 70s, and. The mopar kit will come with a new mpfi intake manifold, but you will need a new 4.0l header for the exhaust.
Do a google search for alabama cylinder heads, they cast new 4.0 heads but they are pricey. I would give you a link but can't right now.
Sent from my DROID2 using Tapatalk

Awesome. Thanks !!

 

[Sasquach]

Yes do a search and you will find all the info you need on this. In a nut shell you want the 7120 head, you can use stock intake but must use a 4.0 exhaust(thats a good thing to).

 

[stoney bones]

just called alabama cylinder....

they offer a new cast 4.0 head for $510 plus $30 shipping

 

[stoney bones]

sasquach, where did you acquire your mopar mpi?

 

[Sasquach]

sasquach, where did you acquire your mopar mpi?

Monicatti motors, they had the lowest price I could find.