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Unread 04-10-2014, 10:12 PM   #1
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1972 J-Series Truck 
Join Date: Mar 2009
Location: CA
Posts: 12
New 1972 J2000 Upgrade

Hey guys! I pulled the trigger and bought myself a J2000 about 3 months ago.

Love the truck so far but are have been debating addressing the power issues. It has the standard 258.

I have done my homework and know that doing a 4.0 head conversion is an option. My one drawback is that my engine has a single barrel carb. Does that mean that I will have to change the intake along with the exhaust. Aka more $$$. I would be putting all this money into the head and then restricting it with the small carb.

Would you guys suggest just dropping in a larger engine and calling that the end of it.

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Unread 04-11-2014, 10:04 AM   #2
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1966 CJ5 
Join Date: Oct 2012
Location: Two Harbors, Minnesota
Posts: 1,099
either the amc 304 or 360 should be about an easy a bolt in as you could hope for. check the axle gear ratio's before you decide as something like 3.07 would make the 360 the better option and if you have 3.73 or 4.10 gears, then the 304 would do as well. also, if you plan on using it for what it was built for, 3/4 ton work truck, i'd go the 360 for the added towing and hauling power. if you're just using it for around town, light trails, etc., then the 304 would be fine.
good luck to you.
1966 CJ5A, mods are coming
1966 Wagoneer, bone stock
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Unread 04-11-2014, 10:47 AM   #3
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1975 J-Series Truck 
Join Date: Aug 2013
Location: Wheatland, Ca
Posts: 15
If close by in CA and decide on a 360. I have one that I am willing to sell. Pulled from a Wagoneer in a pick/pull, so it will have to be gone through.

Last edited by flyingdave; 04-12-2014 at 08:35 AM..
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Unread 04-14-2014, 01:25 AM   #4
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1981 CJ7 
Join Date: Jul 2009
Location: Bali, Indonesia
Posts: 4,272
I have the 258 in the J20 and it is indeed a bit sluggish. However the 258 is a great off road engine and has lots of low down torque to get out of muddy holes. With 4.88:1 gears on 33s the 116hp is OK.

If your basic engine is in good shape you could look at the ignition and carburation, really just to release horses which are penned up in worn out parts.

A 1972 would have points and a cansiter coil and small cap distributor. These can be swapped out for something a bit stronger which will give a consistent spark. I favour a 1979 up Motorcraft distributor with electronic pickup, fairly cheap reman unit, the Teamrush distributor cap and rotor and leads from a Ford 300CI 6 cylider of the early 80s and something for the ICM, probably a module out of a GM HEI unit and lastly a later E-core coil. This may make quite a difference, mainly because you are replacing old worn out parts. This will all cost around $100.

Carburation I would try and find the 1983 up alloy manifold for the 2 barrel from a CJ. They are lighter and better shaped and come with a manifold heater for cold weather. There is a wide choice of carbs from a cheap junkyard Motorcraft 2100 to a Weber 38.

The cylinder head can then be changed to a 4.0 but I have had mixed reviews from those who claim 30hp gains to those who found no change when retaining the carbs and cam. It would be great if you could also fit the mid 1990s Chrysler EFI to the block but you will need a fair few bits to make it work. You could keep the single choke carb, it gives good vacuum signals at low engine speeds.

The head swap is documented here on Jeepforum on the CJ forum and on

Would I go for a V8 instead? A lot more work than it sounds and it is heavier.
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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1995 Cherokee 4.0 - CHEROKEE
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Unread 04-14-2014, 06:51 AM   #5
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1983 FSJ Cherokee 
Join Date: Feb 2007
Location: Pensacola, Fl
Posts: 398
258 good engine and if you decide to build a stroker, you have a best crank. In the mean time, a 4.0 head swap is good. Google it, all kinds of info. I did the swap and loved it. I also pulled a HEI dizzy from a early 80's chevy 6 cyl. After a good cleaning, new rotor and cap, new spring set up, and the cam gear for the 360, it was a good pickup for the Jeep.
When I did the 4.0 head swap, I kept the 258 intake and added a motorcraft 2bbl and the engine really came alive. Swaping in a 304 would not really gain you anythimg since its power and the 258 power are kinda close.
If you have time to read a good long post, search in the YJ form for "4.0 fuel injection for 258". If my laptop was not down I would post that link here, right now on my phone.
If you do decide to do a 4.0 head swap or even add fuel inlection, I have an intake, exhaust manifold, good injectors, throttle body, and injector rail with regulator. Also have a duel exhaust header for the 258.
Right now I am in the process of installing my 4.6 stroker in my 83 Cherokee, been doing that for a year now, slow I know. Feel free to ask questions.
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Unread 04-14-2014, 07:17 AM   #6
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1983 CJ7 
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If you are even remotely on the fence thinking you want more power than the 258, the 360 is almost bolt-in as mentioned earlier and a winner in almost every aspect.

I built a nice 258 for my CJ with FI and a free flowing exhaust, 32's and 3.54 gears and it runs fine, I would not be happy with a 258 in my Cherokee.
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Unread 04-17-2014, 03:38 PM   #7
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1984 J-Series Truck 
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First, if your starter is on the driver's side, it's the small bell pattern motor. Just changing the intake and exhaust to '82 up will make a big difference. The one bbl carb restricts air flow by nearly 50%. If the starter is passenger's side, then you can convert to 4.0L, EFI and all if you score a whole rig '91 to '95 with 5 speed. Then use a D300 or Dodge NP208 for RH drop.
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Unread 07-26-2014, 07:06 PM   #8
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1972 J-Series Truck 
Join Date: Mar 2009
Location: CA
Posts: 12
Does the fact that it has a T14 transmission weigh heavily on the engine swap?

Can a T14 handle a V8?
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