AMC 360 Engine for Sale | OEM Jeep V8 5.9L (1970 to 1991)

Description

Engine Background

The AMC 360 is the longest-lived V8 engine American Motors Corporation ever built, produced continuously from 1970 through 1991, ending its automotive life as the standard engine in the last Jeep Grand Wagoneer that rolled off the line in 1991. AMC introduced the 360 in 1970 as a direct development of the 343 cubic inch engine from the 1966 to 1969 era, increasing deck height and stroke to achieve the larger displacement. Its defining characteristic was straightforward American V8 engineering executed well: high-nickel cast iron block, non-siamesed cylinder bores with water between all cylinders, 2.025-inch intake valves with dog-leg exhaust ports, and 2-bolt main caps that provided more than adequate strength for the engine’s intended operating range.

In AMC car applications (the AMX, Javelin, Hornet, and Matador) the 360 produced up to 290 hp (SAE gross) in 1970. The compression and output fell through the 1970s as emissions regulations arrived. By the late 1970s, the detuned 360 was producing as little as 125 hp. When Chrysler acquired AMC in 1987 and retuned the engine for the final Grand Wagoneer applications, output settled at 144 hp, honest and adequate for a 5,000-pound luxury SUV.

The Jeep Grand Wagoneer with the AMC 360 is the dominant application in today’s used engine market. Grand Wagoneers are having a cultural moment, original examples in good condition regularly sell for $30,000 to $80,000 or more, and the 360 is integral to the vehicle’s identity and value. A compression-tested, rear-main-checked AMC 360 with documented casting numbers is a meaningful find for any Grand Wagoneer restoration.

When Replacement Becomes Necessary

• Oil leak at the rear main seal, the AMC 360’s most common and most chronic issue. The rope-style rear main seal is a known seep point on aged engines. We specifically inspect and report on rear main seal condition before shipping.
• Knock under load, rod or main bearing wear on high-mileage examples
• Low oil pressure at idle after warmup, main bearing wear or oil pump wear
• Oil leaks at the intake manifold and timing cover, common on aged AMC V8 engines
• Loss of compression on one or more cylinders, ring wear or scored cylinder walls
• Rough idle that varies with engine temperature, worn cam lobes on engines run on low-zinc modern oil

Known Issues We Document Before Shipping

• Rear main seal, the AMC 360’s most notorious issue: the rope-type rear main seal used by the AMC 360 is a chronic seep point on aged engines. It is not a catastrophic leak in most cases but is persistent and cosmetically objectionable. We specifically assess and report on rear main seal condition before every unit ships. Aftermarket one-piece rear main seal conversion kits exist and are strongly recommended at installation.
• Oiling system valley line concern on high-performance builds: at sustained high rpm (not relevant for stock Jeep operation), the AMC 360’s oil supply to the front of the valley can be insufficient. This is addressed with the “valley oil line” modification, routing an additional oil line under the intake manifold. This is not needed for normal street and trail driving but is relevant for anyone building a higher-output 360.
• 2-bolt main caps, stock only: AMC never built a factory 4-bolt main block. Stock 2-bolt mains are entirely adequate for street and trail use at stock output levels. For a built engine producing sustained high power, aftermarket main bearing girdles are available.
• Flat-tappet cam ZDDP requirement: all AMC 360 engines use flat-tappet camshafts. Modern low-zinc oils accelerate cam lobe wear. ZDDP additive is essential for sustained operation, particularly on the late-production Grand Wagoneer engines that have already seen modern oil for decades.
• Year and application variation: the 1970 to 1971 360 (high compression, AMC car applications) is significantly different from the 1980s Jeep CJ/Grand Wagoneer 360 (low compression, EFI on final years). Casting numbers and date codes matter for restoration buyers.

AMC 360 Variants by Year and Application

Critical buyer information across the 21-year production run:

What Ships and What Does Not

Direct-Fit Vehicle Applications

Search Terms Buyers Use

Used OEM Versus Specialist Rebuild

For a Jeep Grand Wagoneer restoration, Jeep CJ-7 or Cherokee SJ rebuild, or AMC car restoration on a reasonable budget, a documented used 360 with rear main seal condition assessed and casting verified is the cost-effective path. For a show-quality Grand Wagoneer restoration with collector-grade authenticity, a specialist rebuild with hardened valve seats (for unleaded fuel), one-piece rear main conversion, refreshed bearings, and supporting hardware is the better long-term investment. Specialist AMC 360 rebuilds typically run $4,500 to $7,500 from established AMC/Jeep specialty shops.

Inspection Workflow

• Compression test logged across all 8 cylinders with uniformity reported
• Year and donor application documented: Jeep Grand Wagoneer, Cherokee SJ, CJ-7, or AMC car
• Block casting number documented where available
• Rear main seal condition specifically assessed (AMC 360 signature issue)
• Intake manifold and timing cover seep condition noted
• Valvetrain condition assessed for flat-tappet cam wear indicators
• External oil leak survey at all gasket interfaces

Pre-Purchase Buyer Notes

• Plan a rear main seal conversion at installation: aftermarket one-piece rear main seal conversion kits are available and dramatically improve the chronic seep issue. Inexpensive insurance for a Grand Wagoneer restoration.
• Use ZDDP additive: all AMC 360 engines use flat-tappet cams requiring high-zinc oil. Modern low-zinc oils accelerate cam lobe wear. ZDDP additive is essential.
• Match year and casting to your restoration goals: a 1970 high-compression 360 produces dramatically different output than a 1985 emissions-era 360. Match to your authenticity and performance needs.
• Confirm hardened valve seats for sustained unleaded fuel operation: pre-emissions-era AMC 360s were designed for leaded fuel. Modern unleaded operation requires hardened seat conversion for extended highway use.
• Source intake manifold gaskets in advance: AMC 360 intake gaskets are available but may have longer lead times than mainstream GM or Ford parts. Plan accordingly.

Why Buy From Part Nests

• Year and donor application documented before payment
• Block casting number documented where available
• Rear main seal condition specifically assessed (the AMC 360 signature issue)
• Intake manifold and timing cover seep condition noted
• All 8 cylinders compression-tested with uniformity reported
• Valvetrain condition assessed for flat-tappet cam wear
• No core return required
• Free freight delivery to every state
• 15 day replacement warranty against internal defects
• Call (240) 306-7051 to speak with someone who knows AMC 360 rear main seal conversion options, Grand Wagoneer restoration authenticity requirements, and Jeep CJ versus AMC car variant identification