258 rebuild what would you do

[TOYROX]

I'm with Tezza.
I wouldn't go past the 4.o swap instead.

[frankcj7]

stroke the 4.0 to 4.5 or 4.7using the 258 crank running 2bb 2100 carb or 4bb carb on 4.0 head HEI and headers +mild cam
or rebuild the 258 with the above set up... build it for low end torque not HP...
I got a 258 +.30" 0631 ported 4.0 head 258 std cam factory obdI MPI...love it...

[OKA4wd]

ordered a DUI distributer last thursday got it tuesday (cant complain about that) cost US$299, $99 delivery converted to au = $640 installed today with new leads $200 this thing is huge had my doubts about it fitting. Well made a difference but not much, think the motor is worn only 110,000 on the clock but cant trust that so I think one of them hervey bay engines may be on the cards. Tried to find a way to contact chewy but couldnt figure it out, anyone heard good or bad reports on these. This engine ran bad when I got it wouldnt idle checked the plugs & was amazed it ran at all they looked like they had hornet nests on the electrodes. Changed the plugs for slight improvement then changed the pcv valve which made a huge improvement but still lacking somewhere, assume the deposits on the plugs are ash from burnt oil.

[Old 5]

OKA4wd. The intake and exhaust from 4.2 / 258 with not fit the 4.0. I have a 258 with the 470 off-road avenger, an offenhauser aluminum dual plane water heated manifold and a borla stainless header. I didn't have the cash for the HEI so I subbed in an ac/delco points dist with a Pertronics chip and a blaster2 coil to replace the ailing duraspark Ford system. Been on Jeep for about 10 years and works great. Got a big power jump and driveability is great. I put in a wide band air/fuel digital o2 sensor for carb tuning because the stock avenger is a bit large for the 258 and Holley even states that. I am down 5-6 jet sizes on main and secondary jets both and things work pretty good. I run around 2000 ft above sealevel mostly and it works pretty good even up to 6000 ft. Been higher but it does get grumpy about it.

I now some guys that did the 4.0 head onto the 258 and were pretty happy with that as well. The later curved intake seems to be choice on that setup. Unfortunately I moved away from them and haven't kept contact to be able to provide other details. Computer tuning was a bit of a chore as I remember

Cheers

[frankcj7]

I got a 4.0 head on 258 block rebuilt .030 over I decided to go mpi fuel injection from a donor obd1 '95 xj and various hesco conversion parts... runs sweet and no issues at all! the head flow better than the old 258s... you can run it on carb too... a 2bb motorcraft 2100 from j truck or wagoneer will be a great choice of carb... 4.0 exhust and 4.2 intake if you choose the 2bb carb... HEI a must...😉

Sent from my GT-N7105 using Aussie Jeep Offroad mobile app

[OKA4wd]

with the 470 carby how is the fuel consumption as a review said great carby but uses lots of fuel, 2 suppliers both state they are not suited for towing & 1 also stating not for highway use would you agree with this, I want to use the ute for towing Thanks

[Old 5]

For fuel consumption, been long time since I Ran the numbers on a long drive, most of my wheeling is within 40 miles and its not my daily driver. I seem to recall 18-20 on hiway and dont seem to use anymore than other guys with fuel injection or my 95 zj Definitely is better with the smaller jets and I have done 6-700 mile road trips without issue with this setup. As far as towing I only tow out stuck stuff. ����. Never pulled anything on road. My setup is a 75 CJ w/258, 4spd, 3.73, and 32's. I would recommend putting in a digital air/fuel o2 setup for tuning and to keep an eye on it when towing. 470 is very user friendly and easy to adjust.
Part of the reason I went with this setup is simplicity and being able to limp it out of the bush if something fails. Can always squirt gas into carb and I keep a set of points for tje dist in a vacuum bag if the chip fails.