questions on engine swap???

[kirkandsylvia]

Would a 4.2 I6 out of a 79 cj work in a 96 XJ if I swap over either head and intake..or just intake? I am going to swap out my noisy old motor that I just cant seem to fix, and found a 79 cj 4.2 for sale. Is that a swappable motor?

[bails85]

noit quite sure. but im pretty sure that the 4.0 in the 96 is a better motor than the 4.2 out of the cj.

[6spdYJ]

The block may fit, but the 4.0 block you have is better. The other thing to consider is that the 4.0 requires more sensors such as camshaft position sensor that the 4.2 may not have bosses for. You may be able to swap all of the external stuff from the 4.0 to have it fit. The 4.0 is also made to tighter tolerances overall. This could really add up to some fun if you try to smog it. Especially if some do-gooder runs the numbers on your block. The better move would be to pull the 258 crank and have it cut to fit the 4.0 block. This gives a square bore motor with a flat torque curve. You could use the 4.2 rods and pistons, or get some Keith Black 4.0 pistons with the wrist pins positioned to use the 4.0 rods for a bit more torque and better longevity. Use the right size of injectors and just keep quiet at the smog staion. They won't take the time to check your crank throw. It's crazy though that they panic over numbers.
Out of curiosity, does the 96 xj 4.0 have the stud girdle?

[Guest]

The block may fit, but the 4.0 block you have is better. The other thing to consider is that the 4.0 requires more sensors such as camshaft position sensor that the 4.2 may not have bosses for. You may be able to swap all of the external stuff from the 4.0 to have it fit. The 4.0 is also made to tighter tolerances overall. This could really add up to some fun if you try to smog it. Especially if some do-gooder runs the numbers on your block. The better move would be to pull the 258 crank and have it cut to fit the 4.0 block. This gives a square bore motor with a flat torque curve. You could use the 4.2 rods and pistons, or get some Keith Black 4.0 pistons with the wrist pins positioned to use the 4.0 rods for a bit more torque and better longevity. Use the right size of injectors and just keep quiet at the smog staion. They won't take the time to check your crank throw. It's crazy though that they panic over numbers.
Out of curiosity, does the 96 xj 4.0 have the stud girdle?

x2 what he said.

[kirkandsylvia]

The block may fit, but the 4.0 block you have is better. The other thing to consider is that the 4.0 requires more sensors such as camshaft position sensor that the 4.2 may not have bosses for. You may be able to swap all of the external stuff from the 4.0 to have it fit. The 4.0 is also made to tighter tolerances overall. This could really add up to some fun if you try to smog it. Especially if some do-gooder runs the numbers on your block. The better move would be to pull the 258 crank and have it cut to fit the 4.0 block. This gives a square bore motor with a flat torque curve. You could use the 4.2 rods and pistons, or get some Keith Black 4.0 pistons with the wrist pins positioned to use the 4.0 rods for a bit more torque and better longevity. Use the right size of injectors and just keep quiet at the smog staion. They won't take the time to check your crank throw. It's crazy though that they panic over numbers.
Out of curiosity, does the 96 xj 4.0 have the stud girdle?

if you mean the tray looking thing under the crank mounted by the main cap bearings, then yes.

Well I think you have answered the question of the 4.2...it's out. Now looking for a 4.0 to drop in. I really dont want alot of extra work in this project, more just a R&R.
Anyone seen any good deals on a 4.0 recently? Would even be interested in a short block.

[platnumb4x]

I had a YJ and poured a ton of money into it fixing it up just the way I wanted it. When it came time for the engine I hit a few potholes. I was planning on putting a V8 in it. In California if you replace a motor, the motor needs to be the same year of your Jeep or newer, to pass smog. I am not capable of doing this on my own so I called around and found out this was going to cost me about 20K to do it right. This price did not include axle swaps which I would want to do with a V8. I ended up selling the YJ and bought a TJ. I thought my wife was going to kill me but she got over it.

[Shadly1]

Did you ever find out what the noise was? If it's anything related to the top end, it's all fixable and relatively cheap.

[bails85]

yo kirk just for fun whats wrong with the engine in the 96 now? it shouldnt be a problem. its a good motor to have. if it blew up on u then just try to find a replacement or have that one rebuilt. trust me u dont want to @#$%% with all the wiring and throttle cables and etc. it is a bitch. unless u are very knowledgeable in this area of expertise.

[6spdYJ]

Hi Kirk, I remembered last night that I know a guy with a '98 4.0 sitting in his garage. It has 56,000 miles on it. PM me an offer if you're interested. If you, I'll let him know.

[kirkandsylvia]

yo kirk just for fun whats wrong with the engine in the 96 now? it shouldnt be a problem. its a good motor to have. if it blew up on u then just try to find a replacement or have that one rebuilt. trust me u dont want to @#$%% with all the wiring and throttle cables and etc. it is a bitch. unless u are very knowledgeable in this area of expertise.

to put it in a nut shell...and after this explanation, no pun intended...but it sounds like 4 squirels throwing their accorns around the cage. What I thought might be a stuck lifter, and then maybe a rod bearing, and then to find the timing chain stretched about a half inch or so, none of which seemed to be the problem that a noise would be generated from. So now I am just going to yank the old one out (270,000 miles) and drop a used one with less miles and rebuild the other one.

[OU812]

Check the catalytic converter. A bad one can sound like pebles in a soda can.

[kirkandsylvia]

After talking to 6spdYj the other night, he has hooked me up with a 4.0 with 56,000 on it. The determination of the noise has moved to the rist pins. It's the only thing that I can't see or check without tearing down the motor. So, out with the old....in with the new.

[6spdYJ]

Any news?

[kirkandsylvia]

Any news?

I talked to him, and he is suppose to let me know Wed. There is a small chance he may need the motor for himsef if he cant get his going.
Im hoping he doesnt as my other jeep is out of service till I can find a rebuild kit with the accelerator pump. Jeep #2 down for the count. When it rains....it pours.:poop:

[6spdYJ]

Don't sweat it. He has a scanner for it, he'll be able to get it going. I'll twist his arm for you.