248/a999 to ??? Swap

mbalbritton

mbalbritton

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Joined
Mar 22, 2005
Location
Lakeland, FL
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So, with the 258 knock, I’m looking at a rebuild or swap. Seeing as the wife like the idea of a V8 in her YJ, guess I’m good with that!! 😁

So the hunt begins. I’ve not done an engine swap before. What do I need to know? What are best options, what do I need to know or consider?

Going against all things I feel holy about, I’m figuring a 350/TH400 swap. But I’d love to stick to AMC if possible. 360/400???

What’s the easiest and most cost effective option? Start giving me good options.

Current situation?
258/A999/231/D30/D35 in a YJ. and I live in Florida and this is the wife Jeep. It’s not being driven hard at all.
 
Mac5005 said:
Honestly, for yalls use, I’d swap a 4.0 in, this way it bolts up to your trans, motor mounts, etc.

Worst part is the wiring but it’s not terrible.
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This.

However the 304/360 should be able to use the same bell housing. All of the amc engines will swappy swap like that from what I've been told. Then it's just motor mounts, exhaust, radiator, wiring, probably different lengths for the driveshafts... yeah go with a 4.0.
 
From what I know the 4.0 and AW4 are separate operating systems so the AW4 can be controlled stand alone. RAD has controllers and shifters that can handle that.

I am sure that someone will be along shortly to correct me on that lol
 
mbalbritton said:
I like the 4.0 no doubt. But I’d like to see an Aw4 behind it. So, what does that mean for all components and wiring?
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The aw4 is long. So swaping in the 4.0 and an AW4 means rear shaft issues. The computer on the AW4 is separate like mentioned. Are the Rad controllers auto or are those the manual shift one's I've seen?
 
What about the 350/400 option makes you feel unholy? AMC used all sorts of parts from every manufacturer. If it was cost feasible, you bet your ass they would have been putting SBCs in their CJs. At least that's what I tell myself.
 
willness33 said:
What about the 350/400 option makes you feel unholy? AMC used all sorts of parts from every manufacturer. If it was cost feasible, you bet your ass they would have been putting SBCs in their CJs. At least that's what I tell myself.
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Arguably one of the best and most proven combo options, but ya, it does kinda hurt my feelings to see a Tree-fity in a Jeep. :D... but it does make sense.
 
ghost said:
The aw4 is long. So swaping in the 4.0 and an AW4 means rear shaft issues. The computer on the AW4 is separate like mentioned. Are the Rad controllers auto or are those the manual shift one's I've seen?
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Unless you are spending a lot of time at 65+ on the highway,

No need to swap aw4 to get overdrive, especially considering that YJ is likely 3.07 axle gear.

Yes the rad designs shifter can switch between auto/manual control if you have the tcu unit hooked up. Most people just run it in manual.

I’m suggesting stick with the TF trans without overdrive for simplicity.
 
willness33 said:
What about the 350/400 option makes you feel unholy? AMC used all sorts of parts from every manufacturer. If it was cost feasible, you bet your ass they would have been putting SBCs in their CJs. At least that's what I tell myself.
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Hell sbc are getting harder and harder to find. I’ve had to lower the rev limiter on mine to help preserve it haha 😂 went through a couple one year the. Had to steal the motor out of my 60 impala to make a trip
 
Noel said:
Hell sbc are getting harder and harder to find. I’ve had to lower the rev limiter on mine to help preserve it haha 😂 went through a couple one year the. Had to steal the motor out of my 60 impala to make a trip
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They are. I found a worn out turd of a 99 vortec to build. Machine work and moving parts cost more money than I have to throw at it right now.

@mbalbritton you can always LS swap. Its overdone these days but theres a reason for that. Keep it simple with a terminator x backed by a 4l60 and adapt the 231. It would be about the same complexity as any other non amc v8 swap.
 
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willness33 said:
They are. I found a worn out turd of a 99 vorted to build. Machine work and moving parts cost more money than I have to throw at it right now.

@mbalbritton you can always LS swap. Its overdone these days but theres a reason for that. Keep it simple with a terminator x backed by a 4l60 and adapt the 231. It would be about the same complexity as any other non amc v8 swap.
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Hit up @marty79 if you want to have something to run quicker.

mbalbritton said:
Arguably one of the best and most proven combo options, but ya, it does kinda hurt my feelings to see a Tree-fity in a Jeep. :D... but it does make sense.
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Id suggest a th350 trans. Nothing against a th400, but it is likely overkill for your application.
 
paradisePWoffrd said:
Hit up @marty79 if you want to have something to run quicker
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3weeks on this CJ7 swap is my fastest so far..9 deep now I've gotten pretty quick if I have everything hehe
 
I've done an AMC 360 swap into a YJ with a 258/TF999 combo before. It's beyond easy.
Remove 258 and cut off frame side mounts. Bolt 360 to TF999, weld on frame mounts. Buy HD cooling radiator. Run exhaust. Done.
Drivehshafts won't move, existing wiring needed is there (ignition, alternator, etc). Depending on exact model year, you *may* need to change the fuel supply line to 3/8".
But, I say this as an AMC purist, unless you get a absolutely known good 360, they're at least nearly 40 years old by now. So budgeting a rebuild is a consideration.
Going from the very anemic 258 to a 4.0 HO will feel like a V8 swap. I'm pretty sure there are folks who sell 4.0 swap harnesses where you simply connect constant 12V, switched 12V, ground and power up the fuel pump.
You can keep the TF999 with either the 360 or 4.0 swap, they're terrific transmissions. Worse case is you use a harmonic balancer with the CPS pickup on it as opposed to one installed in the bellhousing.
If it were me, I'd do a 4.0 swap if I did anything aside from installing a rebuilt 258 back in.
 
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While I get the "want" for a V8 for nothing shy of sound alone...

I'd go 4.0L all day long, and if you feel the need for additional punishment (time/$$$$$$/replacing the D35), rob the 258 crank/rods for a stroker :popcorn:

Having said that, Josh wants to setup the red Bullnose with an LS/OD... for twin turbos down the road 🙄
 
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