I only hear about the usual boring carb replacement options for a 4.2 such as the poopy weber, and the tempermental and technical TBI's, but whats this other option, available everywhere the dual port 4 Bbl intake with holley carb? to my inexpirienced melon that sounds like a powerful bulletproof setup. Is there anybody out there in jeep land that knows if it works? and furthermore how big of a suck hole can I strap to this six banger, that new Truck Avenger 670 cfm Holley sure makes me dream at night? Is 670 too much? Anybody know?  

I actually have used the 4 barrel ofenhauser manifold on my 4.2l, but i used a 500cfm edelbrock carb...the reason i went with the 500cfm is because the sales guy i was talking to at the time that i bought it said that the holley truck avenger was too big for the motor...it actually turned out that he was right...even the 500 bogged the motor down a bit until i tuned it as low as i could..then it ran pretty well with a decent amount of extra power...if i were you instead of the holley i would go with the edelbrock and get the offroad carb kit that they have...it works just as good as the holley but is cheaper and won't bog the motor as bad at full throtle....if your looking to buy a 4 barrel manifold i still have the ofenhauser that i am no longer useing...i could sell it to you for like $100 plus shipping and handling...my e-mail is HillJP00@aol.com if your interested.  

unless you put a bigger cam in the 4.2 it won't like a big carb. a good upgrade is the 2100 or 2150 2 bbl motorcraft carb. you need the one off of a small block ford. I took one from a big block and it was way too much carb, it just fell on it's face.

you can find the motorcraft carbs all over the place and are easy to rebuild. Should be able to find a lot of info online about this swap.

how do the motorcraft carbs do off road? good/bad on hill climbs and angles?  

Surprisingly well. Much better than a new Weber.

It's not as good as the Truck advenger, but for about $250 less it's great.

I have a 74 Cj-5 Jeep with a 258 and a 390 CFM holley 4 bbl and it works great and runs great at all rpms and its probably one of the best mods i have done to my jeep. I think its the perfect 4 bbl for that engine and it doesnt bog down at all.  

I agree with the 390 Holley. I've got a '78 CJ-5. Had a one-bbl - yuck!  So I put on the 4-bbl Offy intake and the Holley 390 and love it. Talk about a difference, makes that 258 come alive. It is tunable out the wazoo, and off-road mods are available. It's a simple effective bolt-on upgrade. The electric choke if great. Be sure and add headers so what goes in is able to go out. I got the Holley at either Jegs or Summit, can't remember. Linkage came from the shelf at Car-Quest. The spacer/adapter is a 4-hole phenolic so the dual port feature isn't defeated. Plain-jane off the shelf filter for now. A good ignition upgrade is highly recommended, I went with the TFI 'Juicebox' - major improvement.  I plan on an electric fuel pump and a MSD 6A box. Just received a fiberglass body so those'll have to wait! yee-haw! no mo rust.

690 cfm is way too much for a stock 258, I dont think there is enough cam on the market for one of those, that is a big-a carb.  I would have liked to have gone with fuel injection but my knowledge of those is limited and I wanted quick, easy, and instant gratification.  I can't knock the Weber, a bud has one and likes it.  And I hear the Motorcraft 2100 is pretty good, you just have to be sure you get the correct carb, they made about a zillion different ones and it is sometime hard to identify them. But the Weber and 2100 defeat the purpose of the dual port in my case.