• Hello Guest, we are proud to now have our Wiki online that is completely compiled and written by our members. Feel free to browse our Jeep-CJ Wiki or click on any orange keyword when looking at posts in the forum.

Rebuild or swap engines

Rebuild or swap engines
1

1986 Jeep CJ7

Jeeper
Posts
2
Thanks
0
Location
Jamul, ca
Vehicle(s)
1986 Jeep CJ7 4.2 liter, 258 I6, 4 spd, 4" lift w/ 35" tires, 40k original miles
I have a '86 CJ7 w/ 40k orig. miles w/ carb. I been told I broke a connecting rod. I will need to pull the motor. Should I rebuild my AMC 258 i6 / 4.2l to stock? Look for a donor vehicle W/ 4.0 and EFI and rebuild that? Rebuild the original block and put a 4.0 head on? Then the question is which Which EFI, Mopar MPI or Howell EFI
 
First of all, welcome to the forum!
As to the engine, it kind of depends on how much damage the broken rod did to the rest of the engine. The AMC 258 i6 / 4.2l is a good engine, plus if you keep it the same as you got it (good AMC 258 i6 / 4.2l , not a blown AMC 258 i6 / 4.2l :D) there are no problems adapting things over. If you rebuild the original engine (if possible or even practical), then you know exactly what you have. I don't know what your level of experience is, but when you start swapping engines with something other than the original, you open a whole new can of worms. Plenty of threads on the forum to refer to.
Good luck!
 
WELCOME :chug:
Most of the time a busted c'rod is a blocks 'kiss of death'. You won't know for sure till you do a tear down. The head maybe 'scrap' too.
LG
 
I would bet it's a spun bearing on #6 not a broken rod, mine did the same thing and I've heard about it happing a lot with the AMC 258 i6 / 4.2l . I just did a rebuild they resized the crank and rods and it was pretty straight forward. Oh and :ww:
 
I was under the same dilemma a little more than a year ago, only my AMC 258 i6 / 4.2l wasn't that bad. It had blow-by above 2k rpm and just needing a rebuild. Called around about costs and scope of work for getting it rebuilt. After researching a lot about all of the different options, I decided to swap in a 4.0 OBDII and am very happy that I did. It took more studying and tinkering but in the end, it was totally worth it for me. If removing and re-installing the AMC 258 i6 / 4.2l or swapping in the 4.0 myself, the costs were about the same after selling the AMC 258 i6 / 4.2l and additional tools and equipment that I purchased to complete it.

All together, it cost a couple hundred bucks more for me because I wound up replacing all of the sensors and fuel injectors but isn't necessarily required.
 
What were the circumstances of the engine failure?
AMC 258 i6 / 4.2l tough old bird.
Did it get hot or run out of oil?
Sure somebody isn't trying to steal your low mileage Jeep?
Carbon knock can sound like engine self destructing.
Might be second opinion time....unless there's a hole in the block.
 
:ww: A tear down is you best bet to make a wise decision. What damage :( the rod did will give you a better idea of what to do next. :confused: Your level of abilities will be the next factor. A self rebuild is not rocket science :rolleyes: but one of the most complicated rebuild projects. If you want fuel injection, now would be the time to make this swap. Lots of information on this forum about doing this. Worst case your engine is a pile of junk now and you're not comfortable with a rebuild. :o Time to go to the junk yard and find a good 4.0L engine with fuel injection and low mileage. If you do this, be sure to get ALL of the wiring harness. Either way you have some tough decisions to make and none of them will be cheap. Let us know what you find out. :)

PS: As a side note, your profile shows that you have 35" tires. Make sure you've made the proper suspension and steering modifications necessary for these large tires before you have more expensive problems. ;)
 
Please post pics of rebuild. if possible.:D
 
kaotik1 said:
So how much does a 4.0 usually cost?
Click to expand...

I found four near me. The best two I debated between came from rear wrecked autos at reputable salvage yards. No matter if they were already pulled or not, cost was about the same. Between 300 to 450 for the engine itself including the flywheel and all normally attached accessories, sensors, etc. Wire harnesses, PCM and PDC were extra. I got mine in great condition, pulled, delivered and moved into my garage with the wiring harnesses and PDC for 500. They would have negotiated lower but I told them I was paying their full quoted price so that they would take extra good care of it during the delivery. They did and babied it. PCM was already sold so I got a matching one for 35 + 15 S/H from Georgia or Florida.

Used or fabricated wiring harnesses, if they didn't come with the engine were around AMC 150 -250.

Can search the Carparts Onine Salvage site for different grades and costs around the US.
 
kaotik1 said:
So how much does a 4.0 usually cost?
Click to expand...

So you're not misled by my response, if that is the info you were looking for, the majority of the swap cost is in all of the extra stuff you have to do. Did a quick tally from my records and it was an additional 1,030 for the following; Air intake tube, box, and filter, CPS Sensor Kit instead of tapping the tranny, Upstream O2 Sensor, High Pressure Fuel Pump, Fuel Filter & Regulator, High Pressure Fuel Line, Pilot Bearing, Speed Sensor, Connector and Adapter, YJ throttle cable, custom power steering hydraulic hoses, misc engine oil, filters, coolant, etc, custom exhaust pipe adapter piece and other smaller items.

They don't seem like a lot individually but add up quickly.
 
kaotik1 said:
So how much does a 4.0 usually cost?
Click to expand...

Depends on condition and how much work you do yourownself.
You need to get in touch with a local jeep club and ask'em for input.
LG
 
Neuner said:
I found four near me. The best two I debated between came from rear wrecked autos at reputable salvage yards.
Click to expand...

What ones are you talking about in the San Antonio area? I need to look for some parts too. Any Pick and pulls here?
 
Peanut Butter said:
What ones are you talking about in the San Antonio area? I need to look for some parts too. Any Pick and pulls here?
Click to expand...

All were craigslist ads. 1 was an individual, 3 were an auto repair/salvage shop. All on the South side, imagine that. Got mine from Primary Auto. They were awesome to deal with. Not sure about the P+Ps. Thought I found some at one time but never went by.
 
Since this is a rebuild/swap thread, has anyone tried a stroker kit on a AMC 258 i6 / 4.2l ?

I'd like to get into that but am not sure that is a better price than going with a small block 350 with an adapter to the T-176 ....just wanted to know if it was worth it.
 
cj7eatit said:
Since this is a rebuild/swap thread, has anyone tried a stroker kit on a AMC 258 i6 / 4.2l ?

I'd like to get into that but am not sure that is a better price than going with a small block 350 with an adapter to the T-176 ....just wanted to know if it was worth it.
Click to expand...

I know there has been a lot of hoopla in the past about building strokers out of the 4.0 using the crank and rods from a AMC 258 i6 / 4.2l .
But essentially putting a 4.0 head on a AMC 258 i6 / 4.2l accomplishes the same thing.

And you can customize it however you want....whether its FI or carbed
 
Good thread.....but too bad OP has one post, 3 weeks ago....he won't be back....:eek::eek::chug:

Sorry....just erks me....:chug:
 
You must log in or register to reply here.

Jeep-CJ Donation Drive

Help support Jeep-CJ.com by making a contribution.

Help support Jeep-CJ.com by making a contribution.
Goal
$200.00
Earned
$0.00
This donation drive ends in
0 hours, 0 minutes, 0 seconds
  0.0%
Contribute
Back
Top Bottom