4.0 stroker swap

4.0 stroker swap
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stanthecjman

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Location
British columbia canada (the middle of it anyway)
Vehicle(s)
1982 cj7 will be geting stroked, or a v8
hey everyone id love it if u guys could give me some advise on this as i think im geting in over my head...

im so far out of my knowledge base with this thing that im having to do research to find out what questions to ask so bare with me and i have learnt so much that just thinking about my jeep makes my head hurt :p

first off has anyone ever done something like this in there cj?

so let me give u guys some background info first:
-i have a 1982 CJ7 Laredo with a AMC 258 i6 / 4.2l and a 4 speed(anyone know what it should be?)
- The engine is going on it and i have know i would be rebuilding it over the winter for a year
- originally i was going to just do a rebuild with a 4.0 l head but i bought a 4l block and head combo with a good block on it so it got me thinking about how cool a 4.6ish stroker would be under the hood of my jeep
- so the way i figure it is that its only going to cost a few hundred more to do this then the rebuild if i reuse the crank shaft and connecting rods from the AMC 258 i6 / 4.2l

now the part i don’t have figured out is putting the new engine into my jeep... the engine mounts should be the same right? but what about mounting to the Transmission the bell housing bolts should be the same i think or am i over thinking this and it will all just bolt right up...

and a big, in advance thanks to anyone who read that and has anything to tell me that wont hurt my feelings :p
 
stanthecjman said:
hey everyone id love it if u guys could give me some advise on this as i think im geting in over my head...

im so far out of my knowledge base with this thing that im having to do research to find out what questions to ask so bare with me and i have learnt so much that just thinking about my jeep makes my head hurt :p

first off has anyone ever done something like this in there cj?

so let me give u guys some background info first:
-i have a 1982 CJ7 Laredo with a AMC 258 i6 / 4.2l and a 4 speed(anyone know what it should be?)
- The engine is going on it and i have know i would be rebuilding it over the winter for a year
- originally i was going to just do a rebuild with a 4.0 l head but i bought a 4l block and head combo with a good block on it so it got me thinking about how cool a 4.6ish stroker would be under the hood of my jeep
- so the way i figure it is that its only going to cost a few hundred more to do this then the rebuild if i reuse the crank shaft and connecting rods from the AMC 258 i6 / 4.2l

now the part i don’t have figured out is putting the new engine into my jeep... the engine mounts should be the same right? but what about mounting to the Transmission the bell housing bolts should be the same i think or am i over thinking this and it will all just bolt right up...

and a big, in advance thanks to anyone who read that and has anything to tell me that wont hurt my feelings :p
Click to expand...

I have no answers for you but found some good info for you.
One question, why should the engine mounts be the same? :rolleyes:
Jeep Stroker Motor Information
 
Are you going to use the 4spd Transmission that originally was behind your AMC 258 i6 / 4.2l ?

Lets see wich 4spd you have. You may need an adapter for either one if your going with the stroker.

The T-176 /177 will be able to handle the stroker.

http://www.advanceadapters.com/products/pn-712569/

I dont like the SR4 that was in 80s Cjs


*If you read down to the bottom of the link they say it can be used with the AMC 258 i6 / 4.2l as well. That makes me think you wouldnt need the adapter at all.*
 
Last edited:
Petescj said:
I dont like the SR4 that was in 80s Cjs
Click to expand...
X2. It's a weak tranny, as is the T-4 .

I cant recall if the engine mount bosses are the same between the AMC 258 i6 / 4.2l and the 4.0. That's going to be the big factor on whether or not you can re use your brackets and mounts. The mounts are obviously different because of the 4.0 application into the YJ, TJ, etc.

There are a lot of 4.0 swap writeups out there that address the issues of putting a 4.0 into a CJ. I've never had the desire, so I've never bothered to read any of them. :D
 
I have a 4.0L and aw4 swapped in

Stroker really isn't much different from a swap perspective

The real question is what are you going to do about fuel/ air delivery. The EFI is they only way to go to me. But with a stroker there is a few gotchas. Use a obd1 system is typically easier but you can get less running data out of the computer for tunning than obd2. Lots of stroker threads will talk about this in more detail. Biggest advise is do your research and make sure you read multiple write ups as there is a fair amount of misinformation if you read only 1 source
 
stanthecjman said:
i think my best corce of action now would be to just build a kinda of home brew HP AMC 258 i6 / 4.2l , not a stroker but a .04 over pistons 4.0 l head swap heavier cam. it will be easyer to do better on the budget and probably a more drivabul for the kinda of daily driving this jeep will see...

thanks for all the help guys :chug:
Click to expand...

Another option that is cheap is get a running donor cherokee or TJ and swap over the running 4.0L the engine mount bosses are all the same as AMC 258 i6 / 4.2l mounts and you use CJ AMC 258 i6 / 4.2l mounts, except for the very last generation blocks

Wiring is pretty simple you end up with EFI more HP and better running setup

The back end of a AMC 258 i6 / 4.2l and a 4.0L are the same so your current Transmission will work fine and the computer is easy to trick into thinking the auto is there if you get an auto computer
 
they are not that easy to find here, if at all and if u do they need work, engine or tany is gone or it hit a pole at 100 pluss miles an hr... o well
i wish i had the options of a more populated area but i would rather pay more for jeep parts then live anywere elce then here o o well
 
AussieCJ7 said:
the engine mount bosses are all the same as AMC 258 i6 / 4.2l mounts and you use CJ AMC 258 i6 / 4.2l mounts, except for the very last generation blocks


The back end of a AMC 258 i6 / 4.2l and a 4.0L are the same so your current Transmission will work fine
Click to expand...
That's the info stanthecjman was looking for I believe :notworthy:

If you are interested in building up the block and doing a 4.0 headswap, there are some great threads on here covering a lot of ground. I did the swap with some additional work to the block and ended up with a 300hp AMC 258 i6 / 4.2l /4.0 hybrid that pretty much smoked any 4.0 and the majority of stock V8's :cool:
 
Not sure whether you have decided yet on which block to use, but if you choose to use the AMC 258 i6 / 4.2l and overbore it to 3.955 which is stock + 0.060, you end up with a resulting displacement of 287 CI or about 4.8 liters. A 0.030 overbore results in a displacement of 283 CI or 4.7 liters.

Using a 4.0 liter block with a AMC 258 i6 / 4.2l crank and a + 0.060 overbore gives a bore of 3.935 and a resulting displacement of 284 CI or 4.7 liters. A 0.030 overbore gives a displacement of 280 CI or about 4.6 liters.

The point being that using the AMC 258 i6 / 4.2l as a starting point results in a slightly larger engine. And it gives some extra cylinder wall thickness for the same displacement as the 4.0 liter bored 0.060.

There is a downside to using a AMC 258 i6 / 4.2l however.......there is the issue of mating the 4.0 liter head to the AMC 258 i6 / 4.2l block. This project is covered in detail elsewhere and does not appear to be a huge issue.

The other issue is compression....a larger displacement engine produces more compression for a given cylinder head. Without doing a lot of math, my educated guess is that the resulting static compression would be in the 9.6/1 to 9.8/1 area. And that is nothing but an educated guess based on results from other combination.

Using the correct camshaft can reduce this static compression to a dynamic compression value of under 9.0/1. You might be able to use regular gas with the correct camshaft, timing, and mixture. however, my guess is you would probably end up using premium to be safe.
 
so im going to find out 100% when i get the AMC 258 i6 / 4.2l out of my jeep in the next few weeks, i have a spair 4.0 in the shop right now and the good 4.0 i bought for AMC 150 bucks for the head will be avalabul for pick up soon ill be able to tell if the 4.0 will bolt right up to the trany and since ill be ordering my parts after i pull the engine ill know for shure what engine ill be using eather a stroked out 4.0 or a bored out AMC 258 i6 / 4.2l with a 4.0l head eather way it will bring my jeep back to life and ill be able to turn my 33 sx's again :D
 
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