Hey guys! Thinking about boosting the power of your iMotor 302? One of the most popular and effective ways to do it is by swapping in some Explorer heads. This modification can significantly improve your engine's performance, giving you more horsepower and torque. But before you dive in, let's break down everything you need to know about this awesome upgrade.

Why Explorer Heads on a 302?

So, why exactly are Explorer heads such a hot ticket for the 302? Well, it all boils down to improved airflow. The Ford Explorer, particularly models from the mid-90s to early 2000s, came equipped with cylinder heads that featured a better intake port design compared to many of the stock heads found on older 302 engines. These Explorer heads, often referred to as GT40 or GT40P heads, offer enhanced breathing, allowing your engine to ingest more air and fuel. And as we all know, more air and fuel equals more power!

The design enhancements in Explorer heads directly contribute to increased horsepower and torque, especially in the mid-range. This makes them an excellent choice for anyone looking to improve their engine's performance for street use or even mild racing applications. The GT40 heads, found on earlier Explorer models (typically before 1996), are very similar to the Mustang Cobra heads of the same era. The GT40P heads, introduced later, feature a slightly different spark plug angle, which can sometimes create header clearance issues, but they often offer a slight performance edge due to further refinements in the combustion chamber design.

Upgrading to Explorer heads is a cost-effective way to unlock hidden potential in your 302. Compared to aftermarket aluminum heads, Explorer heads are much more budget-friendly, especially if you can find a set in good condition at a junkyard or through online marketplaces. Plus, they are a genuine Ford part, meaning they are durable and reliable when properly maintained. Many enthusiasts have successfully used Explorer heads in their 302 builds, achieving impressive results without breaking the bank. It's a win-win situation!

Identifying Explorer Heads

Alright, so you're sold on the idea of Explorer heads. But how do you make sure you're actually getting the right ones? Identifying them is crucial to avoid any headaches down the road. Here's what to look for:

• Casting Marks: The most reliable way to identify Explorer heads is by looking for the casting marks. GT40 heads typically have "GT40" stamped on them, usually located on the underside of the head, near the valve spring pockets. GT40P heads, on the other hand, might have "GT40P" or a similar variation. These markings can sometimes be small and hard to spot, so bring a flashlight and a wire brush to clean the area if needed.
• Spark Plug Angle: As mentioned earlier, GT40P heads have a different spark plug angle compared to GT40 heads. The spark plugs on GT40P heads are angled more towards the exhaust manifold, which is the main reason they sometimes cause header clearance issues. If you see spark plugs that appear to be almost horizontal, chances are you've got a set of GT40P heads. This difference is quite noticeable once you know what to look for.
• Valve Cover Bolt Pattern: While not a definitive identifier, the valve cover bolt pattern can offer a clue. Explorer heads use the standard small block Ford valve cover bolt pattern, which is a rectangular shape with six bolts. However, this pattern is common to many Ford heads, so it shouldn't be your only method of identification. Always double-check the casting marks to be sure.
• Intake Port Design: The intake port design on Explorer heads is another distinguishing feature. They have a slightly raised and more rectangular port shape compared to the oval-shaped ports found on many older 302 heads. This improved port design is what allows for better airflow and increased performance.

It's always a good idea to consult online resources and forums to compare photos of known GT40 and GT40P heads with the ones you're inspecting. There are plenty of helpful guides and discussions that can assist you in verifying the authenticity of the heads. Remember, taking the time to properly identify the heads will save you potential problems and ensure you're getting the performance upgrade you're looking for.

What You'll Need for the Swap

Okay, you've got your Explorer heads, now what? Swapping them onto your 302 isn't a direct bolt-on affair. You'll need a few extra parts to make everything work smoothly. Here's a rundown of the essentials:

• Intake Manifold: Explorer heads have a different intake port design than older 302 heads, so you'll need an intake manifold that matches the Explorer head port configuration. Options include aftermarket manifolds specifically designed for Explorer heads or the stock Explorer intake manifold. If you opt for the stock manifold, you may need to modify it to work with your carburetor or fuel injection system.
• Headers/Exhaust Manifolds: If you're using GT40P heads, header clearance can be a challenge due to the spark plug angle. You might need to purchase headers specifically designed for GT40P heads or modify your existing headers to provide adequate clearance. GT40 heads typically don't have this issue and can work with most standard headers for a 302.
• Head Bolts/Studs: It's always a good idea to replace your head bolts or studs when swapping heads. New fasteners ensure proper sealing and prevent potential leaks. Make sure to use bolts or studs that are compatible with Explorer heads and follow the recommended torque specifications.
• Gaskets: You'll need new head gaskets, intake manifold gaskets, and exhaust manifold gaskets. Choose high-quality gaskets to ensure a good seal and prevent leaks. Copper or composite head gaskets are popular choices for performance applications.
• Valve Springs: Depending on your camshaft and desired RPM range, you might need to upgrade your valve springs. Explorer heads can benefit from stronger valve springs to prevent valve float at higher RPMs. Consult with a camshaft manufacturer to determine the appropriate valve spring specifications for your setup.
• Pushrods: It's essential to check your pushrod length when swapping heads. The deck height of the Explorer heads might be slightly different than your old heads, which can affect pushrod length. Use a pushrod length checker to measure and order the correct length pushrods.

Don't forget to factor in the cost of these additional parts when budgeting for your Explorer head swap. While the heads themselves might be relatively inexpensive, the supporting components can add up. Planning ahead and gathering all the necessary parts before you start the project will save you time and frustration in the long run.

Installation Tips and Tricks

Alright, you've got all your parts, and you're ready to get wrenching. Here are a few tips and tricks to make the installation process smoother:

• Cleanliness is Key: Before installing the heads, make sure the block surface and the heads themselves are thoroughly cleaned. Remove any old gasket material, dirt, or debris. A clean surface is essential for a good seal.
• Follow Torque Specs: Always follow the manufacturer's recommended torque specifications when installing the head bolts or studs, intake manifold bolts, and exhaust manifold bolts. Use a torque wrench to ensure accurate and consistent tightening. Overtightening can damage the threads, while undertightening can lead to leaks.
• Use Assembly Lube: Apply assembly lube to the head bolt threads, valve stems, and rocker arm pivots. This will help prevent wear and ensure smooth operation during initial startup.
• Check for Clearance: Before buttoning everything up, double-check for clearance between the valves and pistons. This is especially important if you're using a high-lift camshaft. Insufficient clearance can cause serious engine damage.
• Prime the Oil System: After installing the heads, prime the oil system before starting the engine. This will ensure that all the critical components are lubricated before the engine fires up.
• Break-In Procedure: Follow a proper break-in procedure for your new heads and camshaft. This typically involves running the engine at varying RPMs for a specified period to allow the components to seat properly. Consult with the camshaft manufacturer for their recommended break-in procedure.

Take your time and pay attention to detail during the installation process. Rushing the job can lead to mistakes and potential problems down the road. If you're not comfortable performing the installation yourself, consider hiring a qualified mechanic to do the job.

Performance Gains and Considerations

So, what kind of performance gains can you expect from swapping to Explorer heads? While the exact numbers will vary depending on your specific engine setup, most enthusiasts report a noticeable increase in horsepower and torque. Gains of 30-50 horsepower are not uncommon, especially when combined with other performance upgrades like a better intake manifold and exhaust system.

• Improved Mid-Range Torque: One of the biggest benefits of Explorer heads is the improved mid-range torque. This translates to better acceleration and overall drivability, especially on the street.
• Higher RPM Potential: Explorer heads can also improve your engine's high-RPM potential. The improved airflow allows the engine to breathe better at higher RPMs, resulting in more power.
• Compression Ratio: Swapping to Explorer heads can slightly increase your engine's compression ratio. This is due to the smaller combustion chamber volume of the Explorer heads compared to some older 302 heads. Increased compression can improve power and efficiency, but it's important to make sure your engine can still run safely on your desired fuel.
• Fueling: You might need to adjust your carburetor or fuel injection system to compensate for the increased airflow of the Explorer heads. A richer fuel mixture might be necessary to prevent a lean condition, which can damage your engine.

Keep in mind that the performance gains you achieve will depend on the overall condition of your engine and the quality of the installation. A well-maintained engine with properly installed Explorer heads will always perform better than a worn-out engine with a sloppy installation. Be realistic about your expectations and focus on doing the job right.

In Conclusion

Swapping Explorer heads onto your iMotor 302 is a fantastic way to boost performance without breaking the bank. With improved airflow, increased horsepower and torque, and relatively easy installation, it's no wonder this upgrade is so popular. Just remember to do your research, gather all the necessary parts, and take your time during the installation process. With a little effort, you'll be enjoying a more powerful and responsive 302 in no time. Happy wrenching, guys!