Organ Donor
I have a '91 Wrangler which I love and will never part with. A couple of years ago I bought an '85 GMC 1-ton to plow my driveway. At the time I joked about running it until the doors fell off and then making it a drivetrain donor for my Jeep. This spring it broke down and I had to tow it home with my Jeep and it has been sitting on my front lawn ever since.
Does swapping components from my GMC make sense or will it be more trouble than what the parts are worth? It has a 350 V-8 engine and I'm not sure what the axles are.
Alex
via e-mail
If it's really a 1-ton K-30 4x4 you scored. The 350 isn't anything special. The '85 probably has the Q-Jet 4bbl, which does pretty good off-road. It's worth swapping in your YJ and you can update the induction to a simple TBI injection at a later date if you need/want to. The cylinder heads aren't anything to brag about. Swap 'em to a pair of later-model Vortec heads from a '96-'00 5.7L truck and a Vortec-specific manifold for a 30-40hp boost if you're into power.
The transmission is probably a TH400 if it's an auto or an SM465 if it's a manual. Both are excellent, although neither will give you an overdrive. That shouldn't be that big of an issue since the axle gears in a 1-ton GM truck should be 4.56, which will give you a decent highway rpm with 35s or 37s.
As for the axles, if it's really a 1-ton then it's got a Dana 60 front with kingpin knuckles (easy to put high-steer arms on), 35-spline inner, and 30-spline outer axleshafts. It's a highly-desirable axle. The rear will be a GM 14-bolt. The 14-bolt is super-durable, but the pumpkin hangs low, as I'm sure you can see. You can drop a Detroit Locker in the factory open case easily. It's also one of the cheapest Detroits to buy since it's not a full carrier locker. You can shave the bottom a bit if you're gonna run short tires. Just to give you an idea, a pair of axles like this in stock, but good condition will fetch about $1,000-$1,500/pair used.
The only downside is that the front axle has the pumpkin on the passenger-side and your YJ has the pumpkin on the driver-side. You'll need to swap T-cases if you use the Chevy axle. If you're using the engine and tranny from the Chevy you may as well use the T-case also. In '85, I'm not sure if GM was still using the NP205 or if they'd gone to the NP208 yet on the 1-ton trucks. The NP205 is a burly iron, all-gear T-case and the only disadvantage is that the factory adapter clocks it so the front output shaft drops down very low. At the factory clocking it would make the T-case hang very far below the framerails. You could use an aftermarket adapter on the GM tranny so you could run an earlier Jeep Dana 300 T-case or other model with a passenger-drop front output.
Alabama Slamma
Guys, I have a built Mopar honker and was thinking about putting it in my '78 CJ-7. Do you have any articles on this type of a swap? I have a Ford 9-inch rear axle with disc brakes that I am going to shorten to the wide-track width, a Ford tranny and transfer case, but I am looking for info on the engine conversion. Any info is greatly appreciated.
Sam Wimberley
Satsuma, Alabama
I'll assume you're talking about a Mopar 383/400/440, right? All three have the same bellhousing bolt pattern. Just for clarification, the Chrysler small-blocks, both LA and Magnum share the same bellhousing bolt pattern that's different than the big-block.
As for motor mounts, TransDapt, trans-dapt.com, makes a set to mount a B/RB into a '72-'87 Dodge truck that you could use to get started. It's PN 4565. You could also check Bouchillon Performance, bouchillonperformance.com, for Chrysler hemi, small-block, and big-block swap parts. Again, it's for installation into a Dodge truck, but it will get you going. Nobody I've encountered makes a kit to put a Mopar big-block in a CJ.
For the transmission, if you go manual you'll need the appropriate flywheel and bellhousing for your tranny. The 383 is internally-balanced, the 400 is externally-balanced, and the early 440s before '73 were internally- and '73-later externally-balanced. Lakewood, mrgasket.com, makes a bellhousing that will mount a B/RB to a Dodge NP435 or NV4500 transmission. The NP435s are really strong and are getting more common in wrecking yards. The plus to going with the Dodge NP435 is it's relatively short and already has the 6-bolt, 1x23-spline pattern to mate to a Dana 300 (don't think you'll want to keep the Dana 20 in there, right?).
Finally, you could get a TF727 auto for a big-block Dodge truck and mate it to your T-case.
Building Muscle
I grew up in the 1960's so I had the luxury of owning and hammering on several '67 -'69 muscle cars, most of which were bought for $1,500-$2,000. Having that out of my system, about 15 years ago I decided I needed some sort of a toy with a motor in it.
Long story made short, I have a restored '80 CJ-7 that doesn't see very many off-road miles. The CJ has a fresh 258 and I've spent more money on this jewel than I would have on the customary 350 Chevy. I have a DUI HEI distributor, Offenhauser intake with Holley 390 cfm carb, and a cast exhaust manifold (I hate leaky headers).The thing is still pretty gimpy but very reliable.
I saw this add from Clearwater Cylinder Head advertising a 40hp bolt-on 4.0L HO head for $400 and it has me curious. I asked them if my Offy intake would bolt to this head and they don't know. Why would this single bolt-on give me 40hp? The shop didn't know anything specifics on installation of the head.
Michael Dick
Iowa
I hear ya on the cheap muscle cars. In the '80s (before the Japanese started buying 'em all and driving up the price) I passed on buying a bunch of cheap iron. Still wish I'd bought the $2,600 '57 Chevy with the dual quad Power Pack 283, the $1,800 409-powered '55 Chevy, or the $2,500 440 6-pack GTX with the Dana 60 and manual tranny with the pistol grip.
As for your 258, I don't know about 40hp with just the head alone. Figure bolting a set of better Vortec heads on a 350 Chevy in place of the standard 76cc heads will get you about 30-40hp. That's with almost 100 extra cubes. In reality you may see 25hp at the crank with a stock-cammed 258.
The 4.0L head does flow a whole lot better than the 258 head, especially in the mid-lift flow numbers. If you want to upgrade on the cheap, you can go to the junkyard and pull any '91-'99 4.0L head. To really take advantage of the better flow numbers I'd think about a cam swap. Since you've got to pull the head to remove the lifters in a 258/4.0L engine this would be the best time to do it. A Comp Cams Extreme Energy Xtreme 4x4 X4250H would improve low-end torque and build great mid-range power, but with a 107-degree LSA I wouldn't plan on running it with fuel-injection. If you plan on injection, Comp can custom-grind the cam at no extra charge. Have them grind it with a 112- or 114-degree LSA.
Grab the rockers and pushrods from the 4.0L just to be on the safe side. The 4.0L head will bolt right to the 4.2L block, but there are a few extra water passage holes in the 4.0L head that aren't in the 4.2L block. Use the 4.2L head gasket as a template to determine which holes need to be filled in. Shove some water soluble packing peanuts in the holes to take up some of the space and then use JB Weld or two-part epoxy to fill in the holes. The peanuts will dissolve with no troubles.
You can bolt your 4.2L Offy intake to the 4.0L head, but the 4.2L exhaust manifold has a different bolt pattern. You'll need to use an exhaust manifold or header from a 4.0L. I'd guess that with the camshaft and 4.0L head you'll be close to 40hp over your current setup at the flywheel.