Great Crates

Mopar® crate engines offer a blank canvas so you can kick up your favorite ride any way you see fit. Take it to the streets with Mopar crate engines.

Words: Larry Shepard

Selling a complete engine assembly is not a particularly new idea. Mopar® Performance has been selling complete engine assemblies for about 18 years, starting with the the small block 360 A-engine. These engine assemblies are called crate engines because they are generally shipped or packaged in a large, heavy-duty crate. This somewhat specific segment of the performance parts market seems to have been started by GM and Chrysler (Mopar) and then Ford—Detroit’s traditional Big Three OEMs (Original Equipment Manufacturers). From this unique beginning for an aftermarket part, the crate engine business has grown in leaps and bounds. Today many aftermarket suppliers are involved offering their own crate motors ranging from individual engine builders to traditional suppliers like Edelbrock.

Most Mopar Performance crate engines are typically shipped without a carburetor and without an ignition system but sometimes they do include a distributor and plug wires. Check specific assembly part numbers for details. There are lots of options for a single four-barrel carb selection but don’t overlook the brand-new Edelbrock carbs since they come in small (600–650 cfm) and large (750–800 cfm) sizes. They are readily available and may offer cost advantages. For general street applications, I prefer the AVS versions of the Edelbrock carbs because they offer more adjustability plus potential driveability advantages along with ease-of-adjustment aides. If your assembly is without a distributor, then use a complete ignition kit like P3690426 for the 318-340-360 small block. If you have a distributor, then use a control box like P4120505 (orange – street). Note: both are electronic ignition systems.

Perhaps the biggest news in Mopar Crate Engines is not the amount of horsepower or specific parts detailed (heads, displacement, etc) but the fact that these crate engine assemblies are being shipped (i.e. no current back orders at press time). Note: Crate engines come in a very large box and are shipped directly from the supplier. One of the big advantages of any crate motor is that you get a complete engine assembly by ordering just one part number. This saves a tremendous amount of time and potential development delays to the overall project. A crate motor also defines a specific power and performance level and offers a group of parts that have been developed to work together as a team. As you might expect, crate motors are constantly evolving based on customer requests, so let’s look at some specific assemblies.

The small block 360 A-engine was the first Mopar crate engine and the base model has evolved to the 360 Magnum® base engine and from the original 300 horsepower to 360 horsepower to the current 390 horsepower. The Magnum engine family (1992–2002) is closely related to the “A” engine small block but most parts are unique so use the Magnum Engine performance book (#1473) to sort out details. Note: Performance books by HP Books are available from dealers/WDs like Mancini Racing (www.manciniracing.com) and most large bookstores. The high-performance version of the 360 Magnum crate engine began as a one-horsepower-per-cubic-inch assembly and has evolved to a 390-horspower package (P5155074). The next upgrade is the 410 cubic inch, 6-barrel package rated at 450 horsepower (P5153527). The best and latest 6-barrel information is available from HP Books (#1528) called Six-Pack Engines (includes both small block and big block versions). The biggest of the small block crate engines is the 440 cubic inch version P5153523 rated at 540 horsepower and is based on the special siamesed-bore 340 block and uses a large, 4.18" bore.

For this story, we’ve focused on carbureted versions of crate motors, so the Gen III HEMI® carbureted package is the 392 cubic inch version P5153604 (carb) rated at 540hp. The most economical Gen III HEMI crate engine Mopar now offers is the 6.1L crate engine (P5155067).

The 1964 through 1971 426 HEMI family is now called Gen II. There are three main crate engines based in the Gen II family. The basic 426 HEMI, single 4-barrel package P5249667AE is rated at 465 horsepower. The next step up is the 472-inch HEMI P5249666AE that is rated at 530 horsepower. The biggest of this family is the 528-inch HEMI P5007630AE which is rated at 640 horsepower. These three engines are based on the single 4-barrel intake and carburetor but there are many options. The latest 426 HEMI performance information is available in the 426 HEMI Engine book (HP Books # 1525). Note: Crate engines are constantly being updated with the latest parts, and that causes part number changes and sometimes ratings numbers like horsepower to change.

The top of the engine assembly tends to define much of the appearance. The key to this package appearance lies in the intake manifold. Not everyone wants a single 4-barrel system. Shipping the engine assembly with the intake manifold installed allows the top of the crate engine to be sealed, which helps keep dirt out and decreases potential vacuum-leak problems. Perhaps the most popular intake swap is the 6-barrel system for both the small block and big-block engines. Intakes and carbs, plus all the associated hardware, are available from Mopar Performance. The 318-340-360 6-barrel intake is P4529054 and the big block wedge version is P4529056.

The next option is probably an 8-barrel set-up. This 8-barrel selection still offers choices—inline or cross-ram. Edelbrock offers a dual-plane 2-4-barrel inline intake system for the wedge big blocks (413-426W-440). The 426 Street HEMI engines (1966–1971) used a 2-4-barrel inline system based on two AFB carbs (8-barrel inline intake (P5153737) can also be used in resto applications. New AFB carbs are available from Edelbrock). All these Gen II HEMI crate engines are currently available. Mopar Performance additionally offers a special 2-4-barrel inline intake P4510633 (non-resto use) that features added carb options. In either of these 8-barrel inline systems, which are planned for non-resto/street use, I would recommend using the AVS carbs rather than the original/resto AFB versions. The 426 HEMI also has a 2-4-barrel cross-ram intake (P5007534) available.

All of these crate engines are designed to use pump gas. This means that the cast iron-based engines have about 9-to-1 compression ratio while the aluminum head versions are around 10-10.5-to-1. For racing-only engines, you can use more compression ratio because you use high octane racing gas, which is very expensive and has limited distribution. On the street, you use pump gas. Pump-premium has about 92 octane, which is the limiting factor for engine compression ratios. There is another similar issue with performance engines used in street applications on pump gas. This issue is ignition, but is related to the distributor curve not the total advance. Most performance distributors use a performance curve not a street curve. The typical performance curve yields too much advance at 2,000–2,500 rpm. A street curve wants less spark advance at 2,000 and 2,500 rpm while maintaining the same total advance. Try re-curving performance distributors using spring kit P5153446. Note: There tends to be two spring positions in each distributor, so you can keep a light spring (fast advance) in one position and use a heavy spring in the second position.

Here’s a tip: You do not always want to buy the crate engine with the most horsepower! More horsepower tends to cost more money. Less horsepower tends to offer more fuel economy potential. Remember that increased horsepower and torque can require up-grades to the tires and general chassis that may not fit with the rest of your vehicle package. There are also weight issues with larger engine families. Today there are so many options being offered, try to select the engine that is best suited to your specific needs and budget, not just the one with the biggest horsepower number.