Wildcat 240 Stage 4 Build: Reaper Cam vs Banzai Comparison

Video Credit Red Beard's Garage

In the last 240 build, we left off with the WC22 carburetor, Banzai 265 cam, and a hand-ported WC946 cylinder head. Since then, we have started producing a CNC-ported version of the same Wildcat cylinder, designated as WC946-3. This version features the same 26 lbs springs, stainless steel 31/25 valves, and billet retainers. Our goal was to generate a significant amount of power without the need for expensive cylinder head modifications, billet rockers, chromoly push rods, and hard-welded cams. Instead, we aimed for a combination that would be easy to assemble at a low cost while still achieving high power output.

We have made several changes to the setup compared to the previous version. These changes include the type of head (switched from hand ported to CNC), the carburetors (replaced WC22 with PW24), and the camshafts (changed from Banzai to Reaper). Additionally, we have made some tuning adjustments.

In terms of power and performance, the two combinations may appear very similar when only considering the peak power figures. However, there are notable differences when we examine the complete dyno run.

Camshafts: Banzai Vs Reaper

The Banzai camshaft has arguably been one of the most popular .265 lift camshafts on the market, prompting many other retailers to offer their own versions of a 265 cam. Most of these alternatives are based on the Dynocams CM-Grind. While the Banzai camshaft performs exceptionally well for racing purposes, a comparison of the dyno results reveals that the Reaper camshaft significantly improves in several areas.

What inspired the development of the Reaper Cam?

We began our analysis by examining spec racing engines such as the Briggs Lo206, Ghost 212, and the Tillotson 225RS. The Briggs and Ghost engines are quite similar in specifications and power output, excelling at low-speed power production. In fact, the Ghost 212 demonstrated impressive performance on the dyno, showing better results than most engines tested by Red Beard between 3200 and 4000 RPM.

Both the Briggs Lo206 and Ghost 212 engines engage their clutches between 3400 and 3600 RPM and can operate up to 6100 RPM, providing a 2500 RPM operating range. These engines exhibit a fairly linear power band, peaking around 5100 RPM.

Originally, the Tillotson 225RS had its RPM limit extended by only 400 RPM; however, its clutch needed to engage between 3800 and 4200 RPM because it utilizes a .265 lift camshaft, which shifts the peak torque to a higher part of the power band. To better accommodate this camshaft, the Gen 2 engine was increased to 7500 RPM.

The Tillotson shares characteristics with many engines on the market, particularly when employing a 265 lift cam and a VM22/PZ26 carburetor. If the Tillotson, Ghost, and Briggs all have the same gear ratio and engage their clutches between 3400 and 3600 RPM, the Ghost and Briggs will out-accelerate the Tillotson and many higher horsepower builds for the initial 500-800 RPM. While this may not seem significant, it is a notable difference from typical setups.

In non-racing or recreational applications, stock torque converters and clutches engage at lower RPMs, around 2200-2500 RPM. This is significantly lower than what Red Beard tests, as the disc clutch used engages around 3200 RPM, which is relatively low for a disc clutch.

At 3300 RPM, the Ghost produces 5.8 ft-lbs of torque, the Wildcat 240 with the Banzai outputs 3.13 ft-lbs, and the Reaper yields 9.83 ft-lbs. This means the Reaper generates more than three times the torque of the Banzai at 3300 RPM and nearly double that of the Ghost. Keep in mind that the power figures will be less at 2500 RPM. The Stage 4 Wildcat likely produces a torque value at 2500 RPM comparable to, or possibly exceeding, that of the Briggs, Ghost, or Tillotson at their recommended clutch engagement RPMs, making it much more suitable for aftermarket recreational use due to its broader RPM range.

In addition to producing more power across the board, this engine configuration offers more versatile gearing. 

To illustrate this:

If you use the same 6:1 gear ratio at 3300 RPM, the torque figures yield 34.8 ft-lbs for the Ghost, 18.78 ft-lbs for the Banzai Stage 1, and 58.98 ft-lbs for the Reaper. The Reaper's higher and more stable RPM range allows for increased gear ratios to obtain additional torque, or, conversely, a reduction in ratio for higher speeds.

Here are the goals for the Reaper camshafts:

1. Achieve the best average power between 3500 and 7500 RPM.

2. Generate more torque below 4000 RPM than a stock or mild engine.

3. Provide strong acceleration when engaging the clutch at 2500 RPM.

4. Produce as much or more power than a typical stage three build using a standard 265 camshaft.

What changed in engine tuning?

The camshaft has performed well; however, a slight adjustment in tuning may have affected the engine's overall output. We reduced the ignition timing from 34° to 28°. The 240RS has a compression ratio of approximately 11.5:1, which is quite high for pump gas. We've experienced issues like detonation and blown head gaskets with fuels rated below 90 octane. To address these problems and help the engine run cooler, we decided to pull timing. Although this adjustment may lead to increased power output, it's important to remember that maximizing power isn't always the goal, especially when the gains are not worth the potential decrease in engine longevity.

Additionally, the carburetor is running slightly richer, particularly with a significant dip in performance from 3800 to 5200 RPM and again above 7000 RPM. Using a smaller main jet could resolve the dip at low RPMs and lean the mixture at higher RPMs, allowing the engine to produce more peak horsepower. In our testing, carburetors tend to run a bit richer in non-karting applications. 

For racing go-karts, fuel is drawn from a tank located between the driver's legs, traveling through approximately 2.5 feet of tubing to the fuel pump and then to the carburetor. In gravity-fed applications, commonly seen in mini bikes and various recreational vehicles, the fuel tank is positioned much closer, which may provide additional pressure from the weight of the fuel. This can lead to greater fuel flow compared to the setup in a racing go-kart.

We recommend purchasing a set of jets when buying a carburetor and suggest going down at least one jet size for gravity-fed applications compared to the jet that comes with our carburetors. Keep in mind that tuning can vary due to atmospheric conditions. For more detailed tuning instructions, please refer to our blog section or the product description.

Carburetors WC22 vs PWK 24

In the testing conducted so far, there is little difference in peak power and torque between the two carburetors. The WC22 features a 26mm bore with an oval venturi measuring approximately 23mm by 20mm, flowing about 85 CFM. In contrast, the PWK24 has a 24mm bore with a 23mm diameter venturi that flows about 107 CFM. On the flow bench, the head demonstrates a flow rate very close to 85 CFM at .250 lift; however, the camshaft only allows for about .265 lift, which is not enough to fully utilize the potential of these carburetors at this stage.

Flat Slide or D-shaped slides are expected to atomize fuel better, provide more responsiveness, and generally yield more power, but the overall performance depends significantly on how well the carburetor is tuned for the engine. The PWK is likely to produce slightly more power once the jetting is properly adjusted; however, the WC22 has proven to be very capable of delivering identical power output.

How Does the Wildcat 240 Compare to Other Engines?

The comparison is not straightforward, as many may expect significant power gains in peak torque and peak power. While peak numbers did improve, the results may seem underwhelming to some. This can be attributed to our camshaft design, which focuses on broad power delivery rather than peak power. Although we could have designed a camshaft to favor higher peak numbers, we believe that while many cams on the market can achieve that, very few can produce power effectively in the 2500-4000 RPM range like the Reaper cam, while still delivering similar peak power between 5000-7500 RPM.

Here are some recent tests and comparisons with similar output engines:

The Wildcat 240 Stage 4 ranks as the fifth-highest-horsepower engine, excluding billet heads, and second in peak torque. Our Tillotson 236 kit, combined with the Banzai and WC22 carburetor, ranks second in horsepower and first in torque, securing the best overall performance.

The most intriguing comparison is between the Wildcat 223 and 240, both utilizing the new Reaper cam, CNC-ported head, and PWK24 carburetors. The key differences are in compression, displacement, and ignition timing. The Wildcat 223 produced about three-quarters of a horsepower more, but did so at 1300 RPM higher. Conversely, the Wildcat 240 generated 1.25 ft-lbs more torque and achieved this 1200 RPM sooner. The lack of top-end power in the 240 may be due to reduced ignition timing or the engine's dynamic characteristics, highlighting the importance of testing since not every setup is one-size-fits-all, and proper tuning is vital to maximize the performance of any combination.

The Predator engines represent a more advanced level of assembly, featuring higher lift, larger cams, and ratio rockers, which help achieve higher peak numbers in some cases. Combining the WC946-3 with either the PWK24 or WC22 carburetors and either the Banzai or Reaper cams in the Wildcat 223/240 or Tillotson 228/236 models positions these engines on par with the higher-performing builds. It's worth noting that we have yet to reach the full potential of these Wildcat builds.