The AMC 401 V8 is a legendary powerplant, renowned for its massive displacement and robust torque output that made it a favorite in muscle cars and rugged 4x4s. For enthusiasts and restorers, building a reliable and powerful 401 requires sourcing the right components. From complete serpentine systems that modernize the engine bay to critical internal parts for a rebuild, the quality of your parts directly impacts performance and longevity.
This roundup focuses on essential products designed to help you get the most from your AMC 401. Whether you’re performing a full rebuild or simply upgrading key systems, these components are selected to enhance both power and the legendary reliability that makes this engine so sought after. We’ve compiled a list of top-tier options to help you build an engine that will last for years to come.
Top AMC 401 Engine Components for Your Build
- All Inclusive Serpentine System for AMC Jeep
- ALLOYBOLTZ AMC/Jeep V-8 Stainless Steel Engine Bolt Kit
- JGhyperX 2131 Intake Manifold for AMC and JEEP
- All Inclusive Black Serpentine System for AMC
- AMC Alternator Bracket Mid-Mount 304 360 401 V8
- AMC 401 Engine Rebuild Kit with Sealed Power Pistons
- AMC 401 Engine Gasket Set by Fel-Pro
- AMC 401 Performance Camshaft Kit by COMP Cams
All Inclusive Serpentine System for AMC Jeep
Modernize your engine bay and improve accessory drive reliability with this comprehensive serpentine system. Featuring polished billet aluminum pulleys and brackets that are CNC machined in the USA, this kit adds a significant visual upgrade while enhancing function. The single serpentine belt design is more efficient and easier to maintain than traditional V-belts, reducing the chance of a roadside failure.
This is an all-inclusive package that comes with everything required for installation, simplifying the upgrade process. The product is backed by world-class customer support and a lifetime warranty on all components, providing long-term peace of mind. It is engineered to make your AMC 401 stand out with both its appearance and its performance.
ALLOYBOLTZ AMC/Jeep V-8 Stainless Steel Engine Bolt Kit
Dress up your engine and prevent rust with this comprehensive 239-piece stainless steel hex bolt kit. The 304 stainless steel offers excellent corrosion resistance, ensuring your engine bay looks clean and professional for years. This kit is designed specifically for AMC V8 engines, including the 401, and provides a uniform, high-quality finish.
Organization is made simple as the kit includes individually packaged and labeled component kits for every part of the engine, from the intake manifold and valve covers to the oil pan and timing cover. The inclusion of special thick intake washers and a carb stud kit adds value and completeness. This is an ideal solution for anyone performing an engine rebuild or simply wanting to replace old, worn factory fasteners.
JGhyperX 2131 Intake Manifold for AMC and JEEP
Unlock improved airflow and throttle response with this aluminum dual-plane intake manifold. Designed to operate efficiently from idle to 5,500 RPM, it provides a strong power band that is perfect for both street driving and performance applications. Its dual-plane design helps maintain good low-end torque while allowing the engine to breathe better at higher RPMs.
As a complete intake manifold section for carbureted engines, it is a direct replacement and upgrade over stock cast iron units. The aluminum construction dissipates heat better than iron, which can help prevent vapor lock and maintain a consistent air/fuel charge. This component is a fundamental upgrade for anyone looking to increase the horsepower and efficiency of their AMC 401.
All Inclusive Black Serpentine System for AMC
For a sleek, modern look with superior corrosion resistance, this black anodized serpentine system is an excellent choice. The billet aluminum pulleys and brackets are CNC machined for precision and then treated with a durable black anodize finish. This kit not only looks professional but is also built to last under harsh conditions.
The patented CVF Racing design ensures a simple and straightforward installation process. This kit goes a step further by including a new alternator, AC compressor, and power steering pump, making it a truly all-in-one solution for modernizing your engine’s accessory drive. It is a practical and aesthetic upgrade that significantly enhances reliability.
AMC Alternator Bracket Mid-Mount 304 360 401 V8
This billet aluminum alternator bracket offers a clean and reliable solution for mounting your alternator on AMC V8 engines. Its mid-mount design provides a tidy installation and works with both GM and AMC-style alternators, offering flexibility for your build. The bracket is also designed to be compatible with factory power steering brackets.
Constructed from high-quality billet aluminum, it is both strong and lightweight, adding a custom touch to your engine compartment. The precise machining ensures a perfect fit for vehicles from 1972 and newer. For anyone needing a replacement bracket or looking for a more robust mounting solution, this product is a straightforward and effective choice.
AMC 401 Engine Rebuild Kit with Sealed Power Pistons
A complete engine rebuild requires a foundation of high-quality internal components, and this rebuild kit provides just that. Including Sealed Power pistons, a brand known for its durability and precision, this kit is designed for a reliable and long-lasting engine reassembly. It typically contains all the major internal parts needed, such as pistons, rings, bearings, and a full gasket set.
Using a comprehensive kit like this ensures that all components are matched and designed to work together harmoniously. This is crucial for achieving proper engine compression, oil control, and overall reliability after a rebuild. For any restoration or performance build, starting with a quality rebuild kit is the first step toward a powerful and dependable AMC 401.
AMC 401 Engine Gasket Set by Fel-Pro
The reliability of any engine build heavily depends on the quality of its gaskets. A Fel-Pro gasket set is the industry standard for a reason, known for superior sealing technology and material quality. This set includes all the necessary gaskets and seals to complete an engine rebuild, from head gaskets and intake manifold gaskets to front and rear main seals.
Fel-Pro gaskets are engineered to withstand the heat and pressure of a powerful V8 engine, preventing oil leaks and maintaining proper compression. Using a premium gasket set is a non-negotiable aspect of building an engine for both power and long-term reliability. This component is essential for ensuring your meticulously rebuilt AMC 401 remains leak-free and strong.
AMC 401 Performance Camshaft Kit by COMP Cams
The camshaft is the heart of an engine’s personality, controlling valve timing and directly influencing power output. A performance camshaft kit from COMP Cams can significantly increase horsepower and torque across your engine’s RPM range. These kits are often complete, including the camshaft, lifters, and the necessary valve springs and retainers for a proper installation.
By optimizing the timing of the air and fuel entering and exiting the cylinders, a performance camshaft maximizes the efficiency and power potential of the AMC 401’s large displacement. Whether you are looking for a mild torque increase or a aggressive high-RPM profile, a quality cam kit is one of the most effective single upgrades for generating more power.
Buying Guide: What to Look For in a Used AMC 401 Engine
If you’re hunting for an AMC 401 engine, you’re after one of the most legendary big-block V8s from the 1970s. Known for its massive torque and stout internals, the 401 is a favorite for restorations and performance builds. But since these engines haven’t been made since 1978, buying one is an exercise in careful inspection. Here’s my guide on what to focus on.
First, let’s talk about the block itself. The AMC 401 is a member of the AMC 360/390/401 family, so casting numbers are your best friend. Look for the number 3226743 cast into the side of the block. This confirms it’s a genuine 401. Many 360s were swapped into vehicles that originally had a 401, so don’t trust the car’s badge or the seller’s word alone. Physically check this number. Also, look for visible cracks, especially around the main bearing webs and cylinder walls. A magnaflux test is ideal, but a visual inspection for hairline cracks or previous weld repairs is a good start.
The cylinder heads are another critical area. The best heads are the 1971-1975 casting 3211896 with large, open combustion chambers. Later heads have smaller chambers and lower compression. Pull a valve cover if you can. Look for sludge buildup, which indicates poor maintenance, and check for worn rocker arms and pushrods. The valve stems and guides are also common wear points. If the heads have been off, ask if they were resurfaced; too much material removal can bump the compression to a level that’s not friendly with modern pump gas.
Internally, the 401 came with a very robust forged steel crankshaft and strong connecting rods. The weak point, historically, has been the stock pistons. They are cast and sit down in the bore at Top Dead Center, which is great for emissions but bad for power. Many rebuilt 401s will have aftermarket pistons to correct this. Ask about the bottom end. Has it been rebuilt? If so, what was replaced? New bearings, rings, and a polished or turned crank are what you want to hear. If it’s a supposedly “low-mileage” original, be prepared for potential issues with dried-out seals and gummed-up oil passages.
Finally, consider the ancillary parts. A complete engine with its original intake manifold, carburetor (typically a Motorcraft 2150 2-barrel or aftermarket 4-barrel), and exhaust manifolds is worth more than a long block. The factory cast iron exhaust manifolds are notoriously restrictive, so many have been swapped. Don’t be surprised if they’re missing. When doing your 8 Best Review of the AMC 401 Engine for Power and Reliability research, you’ll find that a well-maintained or properly rebuilt 401 is an absolute torque monster that, despite its age, has proven to be incredibly reliable when treated right.
FAQ
How much horsepower and torque does a stock AMC 401 make?
When new, a stock 1971 AMC 401 was rated at 330 horsepower and a massive 430 lb-ft of torque. However, it’s important to remember that these were gross horsepower figures measured without accessories. By the mid-70s, with increasing emissions controls, the net horsepower rating dropped significantly, often into the 250-260 hp range, though the torque remained impressively high. In a vehicle, the feeling is all about that low-end and mid-range grunt.
Is the AMC 401 a good engine for a performance build?
Absolutely. The foundation is excellent. It has a forged crankshaft, strong rods, and a relatively robust block. The main limitations for big power are the cylinder heads, which benefit greatly from porting and larger valves, and the stock intake manifold. With aftermarket heads, a good intake, and a modern camshaft, a 401 can easily make over 400 reliable horsepower. It responds to modifications very well.
What are the most common problems with a used AMC 401?
The most frequent issues I see are oil leaks from the rear main seal and the valve cover gaskets. Timing chain wear is also common on high-mileage, unrebuilt engines. Because of their age, clogged oil galleries from sludge can be a problem if the engine wasn’t maintained well. Also, listen for piston slap when the engine is cold; the cast pistons can develop a bit of noise before the aluminum warms up and expands.
What vehicles did the AMC 401 come in?
You could find this engine in some of AMC’s most iconic vehicles. This includes the Javelin and AMX for performance, the Hornet SST, Matador, and Rebel Machine. It was also an option in the Jeep Wagoneer, Jeep Cherokee (the full-size SJ model), and the Jeep J-truck series (like the J-10 and J-20), where its torque was a perfect match for a heavy 4×4.
Can I put a 401 in a vehicle that had a smaller AMC V8?
Yes, the swap is generally very straightforward. The 401 shares the same external dimensions and bolt pattern as the AMC 304 and 360. This means it will bolt directly to the transmission you already have. You will likely need to use engine mounts from the donor vehicle or aftermarket swap mounts, and you might need to address exhaust and cooling system upgrades to handle the larger engine’s output and heat.