EC's Stage 4 Wildcat 223 built by Red Beard's Garage

It has been about a year since the last update on the Road to Horsepower for the Wildcat 223. Previously, we used our Stage 3 kit, along with a ported stock head, to achieve impressive results: 15.48 hp at 6600 RPM and 13.57 ft-lbs of torque at 5400 RPM, making it a potent engine.

The Wildcat 223 is back in stock! Originally, there were plans to discontinue it in favor of the Wildcat 240 engine, which offers more displacement. The Wildcat 240 shares the same carburetor and camshaft as the Stage 3 kits, requiring only a billet rod, billet flywheel, and a non-rev-limited coil to complete the Stage 3 setup. However, due to ongoing demand for the Wildcat 223, especially as Harbor Freight has been phasing out the Predator 224 Non-Hemi in favor of the Hemi version, we decided to keep it available.

The Hemi version of the Predator 224 lacks aftermarket support, making the Wildcat 223 the best choice for those competing in the 223/224 class or needing a stock bore size of 70mm, as demonstrated in Red Beard's tests. Additionally, the Wildcat is the only engine in the 223/224 category that offers an electric start option, catering to those who prefer the convenience of starting their engine with a turn of a key. It also features dual charging coils for powering lights and accessories.

The Wildcat 223 Stage 4 kit was highly anticipated following the release of the Stage 3 video. Our challenge was to develop a Stage 4 kit that would not only produce more power but also be relatively simple to assemble. While there are numerous methods to increase power, they often come with high costs and complex assembly requirements.

The primary concern is the valve train. Many builds that have surpassed the power output of our Stage 3 kits utilize higher lift cams, which necessitate significant modifications to the cylinder head, as well as stronger and stiffer valve train components. Previous builds have featured .308 cams, ratio rockers, dual valve springs, and chromoly push rods. Setting up these components correctly requires experience and expertise that the average person may not possess. One of the most frequent questions we receive is regarding the required pushrod length. However, this measurement varies based on several factors, including the base circle of the cam, lifter length, deck height, gasket thickness, cylinder head height, and rocker position and geometry. To create a kit that includes advanced valve train components, we need to account for all these variables for every engine.

To address this issue, we aimed to design a kit that utilizes stock valve train components while still providing a justifiable increase in power over the Stage 3 kit. Here are the components of the Stage 4 kit that made this possible.

WC946-3 31/25mm CNC Ported Head -The Wildcat WC946 has been designed to simplify our cylinder head catalog while providing a more usable range of performance. This head is set up for 31/25mm valves from the factory, and we offer stock-length stainless steel valves. The head is also prepared for porting. If you have the skills and experience, you can port it yourself to save on costs. However, we recommend stage kits for those with less experience, and our CNC-ported head may save time for experienced builders.

One of the main differences among engines lies in their cylinder heads. The Wildcat 223, Ducar/Ghost/Tillotson 212, and Predator 212 each feature unique cylinder hemi heads with different ports and valve sizes. While most non-hemi heads are similar, they differ from their hemi counterparts. Each head responds to porting, which can shift the power higher in the RPM range. The cylinder head has the most significant impact on an engine's performance and powerband.

The WC946-3 cylinder head flows approximately 82-85 CFM at .250 lift. In contrast, most 27mm intake valve heads would struggle to achieve this level of flow, especially at .250 lift. In previous videos featuring the Wildcat 240 and Tillotson 228/236, we used a hand-ported version of this head. We witnessed noticeable performance increases when paired with the .265 lift Banzai cam and stock valve train. Therefore, if you only swap out your stage 3 kit head for this one, you'll experience significant gains in performance. The head comes equipped with 26 lbs springs and billet aluminum retainers.

Tennessee Thunderstix "Reaper" .268 Camshaft – We led the market in .265 lift camshafts with our Banzai camshaft, and since then, the market has become saturated with similar products. Most camshafts available today were designed over 20 years ago for Briggs engines and have not been updated since the rise of clone engines. To address this, we decided to bring camshaft grinding in-house to develop new designs. The Reaper is our first camshaft developed specifically for the WC946 head, as well as for higher displacement and higher compression engines. Our goal was to optimize the combination found in the Stage 4 kit, focusing on achieving the best average power between 4000-7500 RPM while also fine-tuning the cam's peak torque and horsepower. We made minimal compromises in this process.

PWK24EC-1K 24mm Flat Slide Carburetor -The PWK24 is a popular and affordable carburetor known for its performance. It features a D-shaped flat slide, which generally outperforms round slide carburetors. Red Beard's Garage tested this years ago and subsequently decided to use the TM24 carburetor for most of his builds.

On the other hand, the WC22 is a round slide carburetor that flows approximately 85 CFM, which may slightly restrict the cylinder head and limit the performance of the Wildcat 240 in tests with the hand-ported head. In contrast, the PWK24 flows around 107 CFM, allowing it to keep up with the head even at a lift of up to .400 inches. The 24mm bore closely matches the inlet cross-sectional area of the cylinder head, ensuring good velocity and volume. With this setup, we should expect improvements in power and throttle response.

These three components form the core elements of the system. If you have a billet flywheel and a billet rod, adding these parts will complete a Stage 4 kit.

Torch Fine Wire Iridium Spark Plug – The Fine Wire Iridium spark plug provides a better and more consistent spark compared to most other spark plugs. One positive outcome of EPA regulations is the drive toward improved manufacturing and technology. The iridium coating enhances the durability of the spark plug, similar to multi-ground plugs, but without their drawbacks. This coating also allows for a smaller electrode, which helps concentrate the spark. The aim is to improve combustion, benefiting both emissions and performance. In our testing, we consistently observe an increase of 0.25 to 3.5 horsepower in all gas engines. We use a heat range suitable for most applications, particularly for engines with compression ratios between 11 and 12.5.

.960 Karting Exhaust - In previous videos, we tested the engines using the header and muffler from the Ghost 212 accessory kit, which may have slightly hindered performance. Based on our experience, an exhaust with a diameter of .960 inches or larger tends to yield more power, particularly at higher RPMs.

While there is a wealth of information available on exhaust tuning, it can often be quite confusing. In summary, for optimal performance, the intake, camshaft, and exhaust must work together harmoniously at a specific RPM. As with many racing applications, space and fitment constraints can impact how we achieve this balance.

To maximize the benefits of exhaust tuning, it is essential to prioritize airflow first and then resonance. An inside diameter of .960 inches or larger enhances airflow, leading to improved power output. If feasible, operating without a muffler or using a flow-through style exhaust with no baffles is recommended for maximum performance.

Additionally, we are using the same billet flywheel, set to 34° ignition timing, along with the 8281 3.353" billet connecting rod.

Comparing the Wildcat 223 Stage 3 to the New Stage 4

If you cannot port your own head, the Wildcat 223 Stage 3 produces 13.09 ft-lbs of torque at 4600 RPM and 13.48 hp at 5800 RPM. Most Stage 3 engines generate similar power levels. When the stock head is ported, power can increase to 13.57 ft-lbs of torque at 5400 RPM and 15.48 hp at 6600 RPM.

Improving airflow from either the carburetor or the cylinder head results in a power increase, shifting the powerband higher in the RPM range. The camshaft primarily serves to complement these changes.

We observed similar results with the CNC-ported WC946-3 cylinder head. By significantly increasing airflow through the cylinder head and ensuring that the carburetor does not restrict airflow, we achieved better performance.

As shown in the chart, the WC946-3 cylinder head significantly improves airflow. Even with a .268 lift camshaft, the WC946-3 flows at .250 lift nearly as much as a ported stock head does at .450 lift. It almost doubles the CFM (cubic feet per minute) of a stock cylinder head. With flow rates between 82-88 CFM at maximum lift, the WC946-3 matches or exceeds the flow of a WC22 round slide carburetor. Therefore, the PWK24 carburetor, which flows 107 CFM, is used to maximize the performance of this combination. While there are minor differences in the camshaft, most of the performance gains come from the upgraded carburetor and cylinder head. If you want to enhance your Stage 3 kit, you could either purchase just the cylinder head or both the head and the carburetor for significant improvements, especially if you are unable to perform the port work yourself.

The Wildcat 224 Stage 4 produced 13.9 ft-lbs of torque at 6300 RPM, compared to the Ported Stage 3 Wildcat, which generated 13.57 ft-lbs at 5400 RPM, representing an increase of 0.33 ft-lbs of torque, but this occurs 900 RPM later. 

Examining the dyno charts, the Stage 4 consistently produces similar torque throughout the entire power curve, which is unusual since shifting the power band by 900 RPM typically reduces low-RPM torque. If we look at the stage 3 non-ported and the stage 4, the torque is nearly identical from 3600-4000, then from 4000-5000, the stage 3 is barely better, but once the engines get to 5000rpms the stage 4 continues to make torque. The ported stage 3 is makes slightly more torque from 3600-5600rpms but from 5600rpms and higher the stage 4 walks the stage 3 ported. 

The peak power for Stage 4 was 18.01 hp at 7700 RPM versus 15.48 hp at 6600 RPM for Stage 3, resulting in a gain of 2.53 hp, 1,100rpms higher than the previous stage. The RPM range between peak torque and peak power is 1,400 RPM in Stage 4 compared to 1,200 RPM in Stage 3. This combination has broadened the power band by an additional 200 RPM between the peaks, and it offers a power band that is actually 1000 RPM wider than that of the Stage 3 Wildcat with the Wildcat 223 Hemi Ported Head. The amount of power gained and the extended power range were surprisingly significant.

In our experience, many customers lack the necessary tools or ability to port their own cylinder head, which is why the Stage 4 kit exists. Therefore, we should compare Stage 3 as it is with a stock cylinder head. The difference is 0.81 ft-lbs in torque and 4.53 hp, representing a 34% increase in horsepower. 

Remember, horsepower and torque aren’t everything, as the gear ratio plays a significant role. The Stage 4 can easily make up the small torque difference compared to the ported Stage 3 by increasing either the rear gear by 2-3 teeth or by decreasing one tooth on the clutch or torque converter. This adjustment not only helps where the Stage 4 is behind the ported Stage 3 between 3600-5600 RPMs, but it also increases torque where the Stage 4 is much stronger above 5600 RPMs. The extra 1000+ RPMs enable the engine to reach a higher MPH, even with a higher gear ratio, making it overall faster when setup and gearing adjustments are made. 

For example, a 19" tire mini bike with a 6:1 gear ratio at 7000 rpms can reach approximately 66 mph. The average torque of the Ported Stage 3, between 3600 and 5600, is 13.04, which, when multiplied by the gear ratio, equals 78.24 ft-lbs. Stage 4 has a torque of 12.55, requiring a 6.23:1 ratio to achieve the same 78.24 ft-lbs. Using a 10/60 gearing results in a 6:1 ratio; if we switch to a 10/63, we obtain a 6.3:1 ratio, which yields 79.06 ft-lbs, providing a slight edge in torque. However, since we are making peak power at 7700 rpms, we can realistically gear for 8000 rpms, which gives us approximately 72 mph, maintaining the same torque at the axle with about 6 mph more top speed. Also consider the differences above 5600 rpms. Unfortunately, we only have data up to 6600 rpms from the dyno screenshots, but the ported stage 3 from 5600 to 6000 makes an average of 12.9 ft-lbs, which is still good, while the stage 4 makes 13.7 ft-lbs, and when increased by the 6.3:1 gear ratio, results in 86.31 ft-lbs. If the dyno charts included data allowing us to calculate the average torque of the engine, we would further see that stage 4 has a significant advantage over the ported stage 3 and an even greater advantage over a non-ported stage 3. 

Here's how it compares to other engines with similar performance.

The Predator 224 engine has the same bore and stroke as the Wildcat 223, making it the most comparable engine. However, the build specifications of the two engines differ significantly. The Wildcat features more airflow, which is evident in the RPM at which it achieves peak power. In contrast, the Predator 224 delivers more power and torque, likely due to its higher compression ratio of 1.75:1 or more compared to the Wildcat 223 Stage 4. Additionally, the Predator 224 aims to match the airflow of the Wildcat 223 Stage 4 by utilizing increased lift and valve acceleration with 1.2 ratio rockers.

Another significant difference between the two engines is the cost, primarily stemming from the more expensive valve train, carburetor, and camshaft on the Predator 224. Our goal is to produce power comparable to that of the Predator 224 in a simpler and more affordable manner. By utilizing stock rocker arms and pushrods, and maintaining the 26-lb springs and non-welded cam, we aim to make assembly easier and more budget-friendly for the average person. 

Decking the head or using a thinner head gasket would be the following steps to help us achieve this power goal. 

We are eager to see how this setup will perform when the stage 4 is installed in the Wildcat 240, which already produces the same torque at a lower RPM as the built Predator 224 and is only 1.5 horsepower shy of matching it. Since we've increased torque by 0.3 ft-lbs, we believe further improvements could lead to an additional two horsepower, similar to what was achieved with the 223 which could allow us to surpass the Predator 224 in a more streamlined and cost-effective way.