Granted, not every one of these engine-swap candidates will fit the budget or chassis of every Jeep out there, but in our opinion, they're some of the best engines you can sling between your framerails
1. GM LS1What: The LS1 is the all-aluminum version of GM's Gen III engine type found in performance Camaros, Corvettes, the GTO, and an increasing number of GM performance sedans.
Why: The 5.7L LS1 is becoming common in wrecking yards and enjoys a huge amount of aftermarket support - from headers to engine mounts to performance hop-ups. It is child's play to make 400 normally aspirated horsepower with an LS1, and supercharged versions venture deep into the land of 500 hp.
Put it in: The lightweight block and heads make it a natural for any Wrangler or long-nosed CJ, while the distributorless coil-on plug technology makes it ideal for flatties and short-nosed Jeeps as well.
Parts sources: Advance Adapters, 800/350-2223, www.advanceadapters.com; Turn Key Engine Supply, 760/941-2741, www.turnkeyenginesupply.com; GM Performance Parts, 800/883-4716, www.gmperformanceparts.com; Painless Performance, 817/244-6212, www.painlesswiring.com; Street & Performance, 479/394-5711, www.hotrodlane.cc.
2. GM LT1What: The LT1 appeared in the Chevy Corvette in 1992 and quickly found its way into Caprice cop cars and Buick station wagons until the LS engine family supplanted it.
Why: The second-generation GM small-block came out of the box with anywhere from 260-300 hp and responds well to performance hop-ups. Like all Chevy small-blocks, every part in the world is available for it and it's easy to make over 400 hp with just a cam and cylinder-head swap.
Put it in: Like the LS1, the lack of a rear-mounted distributor facilitates installation in cramped engine bays. The Optispark distributor mounts through the water pump.
Parts sources: Advance Adapters, 800/350-2223, www.advanceadapters.com; GM Performance Parts, 800/883-4716, www.gmperformanceparts.com; Painless Performance, 817/244-6212, www.painlesswiring.com; Street & Performance, 479/394-5711, www.hotrodlane.cc.
3. Chrysler 5.7L HemiWhat: Reintroduced with much fanfare in 2003, Chrysler's aluminum-head 5.7L Hemi makes anywhere from 330-345 hp in factory trim.
Why: Deep-breathing hemispherical combustion chambers pull freely past 6,000 rpm if you do away with the factory rev limiter, and a simple Competition Cams cam swap and electronics recalibration gets you deep into the 400hp range.
Put it in: A distributorless coil-on plug ignition and standard Chrysler/Jeep bellhousing bolt pattern make it a cool swap for Jeeps getting a tranny swap too. The fly in the ointment is the pesky fly-by-wire throttle body, but the aftermarket is working on it.
Parts sources: Advance Adapters, 800/350-2223, www.advanceadapters.com; Mopar Performance,www.moparperformance.com; Painless Performance, 817/244-6212, www.painlesswiring.com; Street & Performance, 479/394-5711, www.hotrodlane.cc; Teraflex, 801/288-2585, www.teraflex.biz.
4. Jeep 4.0LWhat: Introduced in the XJ in 1988 and designed after Chrysler's 2.5L four-cylinder, the 4.0L inline-six has proven to be a torquey powerhouse with a reputation for durability.
Why: Widespread parts availability and interchangeability with current Jeep chassis and drivetrain components make it a natural choice for those not needing more than 190-250 hp in a dependable package.
Put it in: Any Jeep chassis that accommodates the 232 or 258 inline-six.
Parts sources: 505 Performance, 505/333-2600, www.505performance.com; Golen Engine Service, 800/591-9171, www.golenengineservice.com; Collins Bros Jeep, 800/699-5337, www.collinsbrosjeep.com; Quadratec, 800/745-2348, www.quadratec.com; Painless Performance, 817/244-6212, www.painlesswiring.com.
5. Ford 302 H.O.What: The Ford Mustang 302 H.O. is an injected iron block and head powerhouse that is among the lightest and smallest iron V-8s offered.
Why: With a baseline of 225 hp, it's easy as pie to make these little brutes 450hp smokers. Plus, the high nickel blocks and moly rings make for a high-mileage, high-revving screamer that easily fits the engine bay of any Jeep out there.
Put it in: It's a natural for the flattie owner wanting real power from an injected package, a sand Jeep, or a rockcrawler that needs razor-sharp throttle attacks.
Parts sources: Advance Adapters, 800/350-2223, www.advanceadapters.com; Ford Racing Performance Parts, 586/468-1356, www.fordracingparts.com; Painless Performance, 817/244-6212, www.painlesswiring.com.
6. Buick 225 V-6What: A 90-degree odd-fire torque monster found in early '60s GM cars and '66-'71 CJ-5 and CJ-6 Jeeps.
Why: The 225 V-6 will idle down to 50 rpm, gets great mileage, delivers more than enough torque for an early Jeep, and is just plain fun to drive and listen to.
Put it in: It's a factory fit in any CJ-5 or CJ-6 and drops right into a flattie. FCs and other oddball Jeeps can benefit as well.
Parts sources: 4Wheel Drive Hardware, 800/555-3353, www.4wd.com; Advance Adapters, 800/350-2223, www.advanceadapters.com; GM Performance Parts, 800/883-4716, www.gmperformanceparts.com; Kenne Bell, 909/941-6646, www.kenne-bell.com.
7. Viper V-10What: Forget the heavy iron truck stuff, we're talking 488 inches of all-aluminum Viper engine from Mopar Performance
Why: Sheer and overstated overkill. There aren't too many with the bucks or room to shoehorn in the big V-10, but at 450 hp and 495 lb-ft of torque - with over 400 lb-ft off idle - the Viper V-10 makes a statement that's hard to ignore
Put it in: We see 'em in Wranglers now and then, but this engine screams for a fullsize J-Truck, Wagoneer, or M-715.
Parts sources: Mopar Performance,www.moparperformance.com.
8. Caddy 472/500What: The biggest of the GM big blocks, they're littering any junkyard in the nation as you read this.
Why: They're the lightest of all the big blocks, yet make crazy torque all day long. The bellhousing pattern and starter location are the same as a Buick V-6 or V-8 to facilitate installation in early Jeeps.
Put it in: They're a tight fit in a flattie or short-nosed CJ, but they fit nicely in later CJs and FSJs. We'd bolt one in place of a Buick-powered FSJ and have lots of fun smoking the balloons.
Parts sources: Maximum Torque Specialties, 262/740-1118, www.500cid.com.
9. RamJet 502What: GM Performance Parts' aluminum-headed, fuel-injected crate engine.
Why: Bolt it to your chassis, hook up 12-volt power to the computer, add fuel, and you've got 502 hp and 565 lb-ft of torque on tap instantly. It's a vicious-sounding mill that bites worse than it barks.
Put it in: We'd love to see an early two-wheel drive Jeepster with the injection manifold peeking through the hood.
Parts sources: GM Performance Parts, 800/883-4716,www.gmperformanceparts.com.
10. Nelson Racing Engines twin-turbo, pump-gas enginesWhat: Shown in the lead photo of this article is Hot Rod Magazine's 408-cube small-block Chevy that churns 1,025 hp on 91-octane pump gas and 1,482 hp on race gas.
Why: Nelson Racing is famous for belting out unbelievable power from incredibly streetable combinations. If you've got the bucks, the company can put a 3,000hp pump-gas engine in your vehicle with a glass-smooth idle that can cruise all day and won't overheat in traffic.
Put it in: Anything you got.
Parts sources: Nelson Racing Engines, 818/998-5593,www.nelsonracingengines.com.