Cj engine swap - JeepForum.com
 
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post #1 of 12 Old 02-12-2015, 08:12 PM Thread Starter
artoy
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Cj engine swap

Hey guys I got a 1980 cj7 with the gm 151. I want to put a 4.0 from a 86 cj in. If I get the t5 with the 4.0 how hard is the swap? What am I looking at?

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post #2 of 12 Old 02-12-2015, 08:34 PM
Mike Romain
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Quote:
Originally Posted by artoy View Post
Hey guys I got a 1980 cj7 with the gm 151. I want to put a 4.0 from a 86 cj in. If I get the t5 with the 4.0 how hard is the swap? What am I looking at?
You need a 91 or newer YJ to get a 4.0. You have to get the tranny too, neither the 4.0 or the CJ 4.2 will fit your bell housing.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #3 of 12 Old 02-12-2015, 11:20 PM
ThisGuyUKnow
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Quote:
Originally Posted by artoy View Post
Hey guys I got a 1980 cj7 with the gm 151. I want to put a 4.0 from a 86 cj in. If I get the t5 with the 4.0 how hard is the swap? What am I looking at?
Wait... What? Do you mean you want to put in a 4.2 from an 86 cj in or do you mean you have a donor cj that someone swapped a 4.0.

There are a lot of variables that need to be covered to truly answer your question, the most important being your skill level.

There are a zillion engine swap threads that deal with native engine swaps and a great source for information at Novak adapts website.

1985 CJ7 Laredo, 4.0, NV3550, D300, 3.31 AMC 20 w/trac loc
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post #4 of 12 Old 02-14-2015, 03:03 PM Thread Starter
artoy
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I'm a professional mechanic. I was planning on getting a t5 to go with the 4.0. I thought cj7s came with 4.0s. Is that not true?
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post #5 of 12 Old 02-14-2015, 03:12 PM
amcfanatic
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Simple solution, the 4.2 is the old AMC 258 (a good engine to start with) The 4.0 is essentially the same engine with some modern upgrades. Either one will work fine in your swap. You will need to get the transmission from your donor vehicle or from some other place as stated above the bell housing from the 151 will not work (Chevy bolt pattern) and the SR-4 won't survive for very long (if at all).

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post #6 of 12 Old 02-14-2015, 03:14 PM
Fingers302
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[QUOTE="artoy" I thought cj7s came with 4.0s. Is that not true?[/QUOTE]

No. CJs were 4.2's

Fingers
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post #7 of 12 Old 02-14-2015, 04:28 PM
Mike Romain
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I'm a professional mechanic. I was planning on getting a t5 to go with the 4.0. I thought cj7s came with 4.0s. Is that not true?
You can bolt a 4.0 up to a T-5, you just have to swap the pilot bearing for a pilot bushing in the crank end. I have that swap in mine from a 93 Grand Cherokee.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #8 of 12 Old 02-14-2015, 09:31 PM
zhopperz
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Hey, Artoy, I swapped the 4.2, in my 81 CJ7, for a stroked 4.0 and am VERY happy with.. I'm running the stock T-176 4speed CJ tranny, and love it.. The 4.2 type crank in the stroker didn't need any pilot bearing mods either. (just used the OEM 4.2 type pilot bearing)..
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post #9 of 12 Old 02-14-2015, 10:49 PM Thread Starter
artoy
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I'm just kinda looking for things I might've overlooking. Like I know I'm gonna need a new radiator but with the alternator carry over? What about the power steering pump? Will stock motor mounts work or will I have to get the ones from the 4.0? And if I have to get the ones from the 4.0 will they mount in the same holes? The new engine comes with a harness and computer. What's the computer for? The carburetor? I'm just trying to grasp the whole job because I don't know anyone who's done it. Thanks guys
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post #10 of 12 Old 02-15-2015, 06:32 AM
Mike Romain
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Originally Posted by artoy View Post
I'm just kinda looking for things I might've overlooking. Like I know I'm gonna need a new radiator but with the alternator carry over? What about the power steering pump? Will stock motor mounts work or will I have to get the ones from the 4.0? And if I have to get the ones from the 4.0 will they mount in the same holes? The new engine comes with a harness and computer. What's the computer for? The carburetor? I'm just trying to grasp the whole job because I don't know anyone who's done it. Thanks guys
You have to realise that there are 2 distinct 6 cylinder Jeep engines and neither is compatible with your existing setup. You have GM stuff now.
The 4.2 is a carb engine usually with V-belts that went into the CJ. The 4.0 is a fuel injection engine with a serpentine belt that went into the YJ.
You have a CJ frame, so you need CJ mounts to match that and the 4.2. The 4.0 will bolt up to the 4.2 mounts.

I am not sure if anything from the 4 banger can be crossed over.

I swapped a 4.2 to a 4.0 and all my 'stuff' swapped over like the intake and carb and the V-belt front end and components. Had to use a 4.0 exhaust header and get an electric inline gas pump. The 4.2 has a mechanical pump, 4.0 is electric.
I chose to stay carbureted.

Good luck.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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post #11 of 12 Old 02-15-2015, 10:25 AM
ThisGuyUKnow
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Quote:
Originally Posted by artoy View Post
I'm just kinda looking for things I might've overlooking. Like I know I'm gonna need a new radiator but with the alternator carry over? What about the power steering pump? Will stock motor mounts work or will I have to get the ones from the 4.0? And if I have to get the ones from the 4.0 will they mount in the same holes? The new engine comes with a harness and computer. What's the computer for? The carburetor? I'm just trying to grasp the whole job because I don't know anyone who's done it. Thanks guys
Again you aren't being clear on what engine your going to use. If your donor is an 86 cj7 and assuming it is stock then your looking at a 4.2 and everything should be natively compatible with your cj. Just literally un bolt it from one cj and bolt it in another.

If you want a 4.0 specifically you'll need to find an engine from a 91 or higher jeep model with the 6 cylinder. The yj had the 258 until the 91 year and the xj Cherokee had the renix 4.0 until 91 year. Generally the renix 4.0 is regarded as inferior to the later high output version that was v introduced in 91.

1985 CJ7 Laredo, 4.0, NV3550, D300, 3.31 AMC 20 w/trac loc
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post #12 of 12 Old 02-15-2015, 04:01 PM
zhopperz
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Artoy, I'd advise trying to find a tranny with the Dana 300 attached.. There are several varieties on the CJ.. You can mate just about any engine with adapter bell housings from Advance... They even offer one with a pre-cut hole, for the crank-sensor, in case you want to do fuel injection now or later...
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