4.0 head on a 258

[STOMPR]

Can you put a 4.0 head on a 258 and it still be IM legal ?

[AKLJ8]

I'm sure Kelly will chime in with the answers but I would guess if the rig is old enough it's exempt. If not I think it has to all be original engine components...

[socalrat22]

this might sound dumb but what if you replace a 4.0 HO with A 4.0 HO?

[erikb]

Kelly probably won't be chiming this week. But.. If you kept the original I/M components intact by using the factory intake it should fly and in fact probably wouldn't even be noticed by the inspector unless you told them.

The real question is why you would want to drive anything with a 258 in it during the winter anyway?

[STOMPR]

The real question is why you would want to drive anything with a 258 in it during the winter anyway?
Is this a real question?

[AKLJ8]

The real question is why you would want to drive anything with a 258 in it during the winter anyway?
Is this a real question?

My 258 runs just fine as a daily driver... But I do have the injection kit on it. The question should be do you want to run the crap Carter BDS carb at all....

[AKLJ8]

If you want to do a 4.0 head swap on a 258 I can help you out. The main thing is capping the waterjackets in the head that wont match up on the 258 block. There are write ups on line about doing the conversion and most people seem to use an epoxy filler and mill the head smooth after words. If your bottom end is in good shape it's a good option. Other wise I'd say just drop in the whole 4.0 and save your self the time of dealing with the head.

[STOMPR]

Well the thing is I have a perfectly good 4.0 head floating around and I should be able to get a complete 4.2 for free in a car. I would then want to have the short block rebuilt of coarse and take care of the water jackets in the head. Of the three methods I have read about online to correct the water jackets Weld, Epoxy, or drill and fill I seem to like the idea of the later best, drilling them out and filling them with freeze plugs.

[AKLJ8]

Shoot.... If your going to do the bottom end anyway grab the 4.0 block i don't use and put the 258 crank and rods you have in it. For $200 I can get you a set of cast Keith Black pistons with a 28.3 cc dish that will give it about 9 1 compression. with .030" milled of the block. Run every thing stock with 4.0 injection and you should be IM legal. Thats basically what I'm doing...

[erikb]

The real question is why you would want to drive anything with a 258 in it during the winter anyway?
Is this a real question?


Why yes it is, IMHO the only CJ with a wheelbase long enough to drive safely in the winter would be the 6 or the 8 and there ain't very many of them runnin' around. If its in a J-truck then you need to be swapping more than just a 4.0 head on.

[holeski]

If your going though all that you should grab the 258 race prep Egale rods I picked up from AKCJ8.
The stock 258 rods are trash and won't hold up for long with higher HP.
Here. http://www.arcticoffroad.com/index.php?option=com_smf&Itemid=26&topic=1567.0

I'm not going to do anything with them anytime soon.

[AKLJ8]

If your going though all that you should grab the 258 race prep Egale rods I picked up from AKCJ8.
The stock 258 rods are trash and won't hold up for long with higher HP.
Here. http://www.arcticoffroad.com/index.php?option=com_smf&Itemid=26&topic=1567.0

I'm not going to do anything with them anytime soon.
For anyone thats interested in these here is some info I got from the shop I got them from in the lower 48.

Eagle had these listed as a JEEP 4.2L 258ci rods .025 long, I beleive that is a typo and these are actually .275 longer than the stock 4.2L 258 rods, and .025 longer than the stock 4.0L 242ci. Eagle 4340 H-beam rods part # CRS6150A3D, FULL FLOAT, Bushed piston pins, 7/16 ARP 190,000 psi bolts.
Stock 4.2L / 258 rods were 5.875" and the stock 4.0L 242 rods are 6.125"

The majority of my customers have been ordering special order pistons, these are FULL FLOAT BUSHED pins and require full float pistons, THESE CAN NOT BE USED WITH PRESS PIN PISTONS.

These rods retailed over $500. These rods are now discontinued and once they are gone, THATS IT! This is is for 1 set of rods, this is for a 6 Cylinder, there are 6 rods to a set. These are Eagle Specialty Products H-beam rods and yes these are BRAND NEW in the BOX!

I can have custom pistons made by ROSS depending on your application, your cost $450 to $500 for pistons, pins & locks.

2 piece forging for increased strength!
Heat treated, Certified 4340 Steel, vacuum degassed to remove impurities.
All surfaces are 100% machined and Shot peened to stress relieve material.
4340 specs allow a range of different materials.
EAGLE uses a higher content of Nickel & Chrome which increases the strength & life of the rod!
Precision alignment sleeves positively locate the rod cap, maintiaining big end bore size and eliminating cap walk.
X-rayed, sonic tested, magna-fluxed, 100% machined with extremely tight tolerances
Silicon bronze bushings for floating pins.
The 3-D stroker design offers reduced weight with no sacrifice in strength.
Sized and Finished in the USA!!

Eagle has become the LARGEST after-market connecting rod manufacture in the WORLD! Eagle manufactures over 125 different connecting rods, and 130 different crankshafts! Eagle never compromises quality for a lower price. All Eagle Steel is batch CERTIFIED! And Eagle NEVER uses recycled materials! Eagle prices are kept low through efficiency in manufacturing processes, improved machinery, large scale manufacturing and HUGE purchasing power of raw materials.

Eagle 4340 steel crankshafts feature EXCEPTIONAL STRENGTH and UNSURPASSED QUALITY at the best price. The perfect choice for demanding applications!

[mousee]

Why yes it is, IMHO the only CJ with a wheelbase long enough to drive safely in the winter would be the 6 or the 8 and there ain't very many of them runnin' around. If its in a J-truck then you need to be swapping more than just a 4.0 head on.


not so much "safely" as people don't know how to drive. I PREFER a short wheelbase in winter. safer and more fun :)

[erikb]

You and I have very different definitions of "safer" then. For me ability of the front end to pass the back end in less then .5 seconds is not a good thing.

[4x4_MMMH_4x4]

too many people just dont know how to drive period... short or long wheelbase... makes you wonder what they did with there drivers ed book or how they passed their drivers test... not that im much better, i drive like batman everywhere, but at least im attentive... some people dont even use turn signals let alone have brake lights turned on... enough of my rant on to the topic...

[mousee]

You and I have very different definitions of "safer" then. For me ability of the front end to pass the back end in less then .5 seconds is not a good thing.



again, boils down to driver. I have never UNINTENTIONALLY swapped ends. never even came close. but I have also been getting sideways in vehicles since I was a children. Rallyin' in the mountains of California was how I learned to drive. If your not sideways, your not driving! lol anyway, I don't want to hijack this anymore. back to our regularly scheduled thread :)