EC's Tillotson 228R stroked to 236cc and ported.

The Tillotson 228R is a complete crate engine designed and assembled here at EC. It is our flagship engine and is very successful. The engine has recently been upgraded with the WC946 Wildcat big valve head. In the previous 228R video, Red Beard showed how much power the engine made from our workbench. The engine is test-fired, and idle adjustment is preset. 

One of the most frequent questions is how much difference there is between the 228R and the 236R. The 236 has 2mm more stroke, and as we've covered many times, adding stroke increases displacement, piston speed, mechanical leverage, and compression. The significance is one change that makes many small changes. Unlike a camshaft or carburetor, adding stroke does many beneficial things at once. 

In the video, we wanted to show that the 228R has more potential for customers when they buy the engine without replacing components. It's safe to say that all engines produce more power when the cylinder head is ported. The WC946 head has large stainless steel valves that give the head more flow potential than smaller stock valves. For example, the ported WC946 flows at .250 lift, which is what a ported Wildcat hemi flows at .400. We have already tested the same ported head on the Wildcat 240RS. It's time to see how it performs on the 228R and, later, how it improves performance on the 236R.

We also want to compare the 228R, 236, Wildcat 240RS, and previously tested engines on the Road to Horsepower that make similar horsepower. 

EC’s Wildcat 240RS, Tillotson 228R & Tillotson 236R

• WC22 26mm round slide carburetor
• 265 Banzai Camshaft
• EC Billet rod
• EC Billet flywheel
• WC946 31/25 ported head w/26lbs springs 

The cam, carburetor, and flywheel are the same as our stage 3 kits; the only difference is the connecting rods that fit each engine. We listed the WC946 head, but it comes on these engines rather than being used as a replacement part. 

Red Beard's Predator 212 Hemi

1. TM24 Mikuni Flat Slide Carburetor

2. 1.2 Ratio Rockers

3. CL-308 Cam

4. Chromoly Push Rod

5. ARC BIillet Flywheel

6. ARC Billet Rod - 212 Version

7. EC 223 Stroker w/EC Billet Rod

This engine was updated with our 223-stroke kit, which helped it produce more torque and similar horsepower. We will post both sets of power figures. However, we want to remember that many believe that the Predator 212 or any 212 is still a viable option since its low starting cost allows more budget for more expensive and presumably better-performing parts. We believe it has already been proven that starting with a 223/224 is less expensive than stroking a 212 to 223 and that larger displacement engines continue to make more low-speed torque and a bigger, broader powerband. Still, in case you haven't watched those videos or read those blogs, we wanted that context here for further comparison. 

Red Beard's Stage 4 Predator 224

• Stage 4 Head (Stainless Valves: 28.5mm intake, 25mm exhaust, Dual springs with billet retainers, 40lb Valve springs. Fully ported and polished, Milled .065" resulting in a smaller combustion chamber, Lash caps, and spark plug clearance washer included)
• Fire 265 (265 lift 246 Duration)
• 1.2 gage roller rockers (total .318 lift)
• 24mm TM24mm Flat slide Carburetor
• Chromoly pushrods
• MSD wire hot coil
• Arc Flywheel
• ARC Billet rod

Many would consider the Predator 224 fully built, as nearly every component has been modified or replaced with an aftermarket component. Arguably, you could go with a 28mm carburetor, a bigger cam, and even a Wiseco piston, which would say this engine has no other beneficial options and would be truly fully built. However, the specs and components list are much more than any other engine we've compared, especially in this blog. 

All of these engines produce close to 18hp and 15ft-lbs of torque. Their cost and components reflect how easily or efficiently the engines can produce this power. As stated, the Predator 224 is near its limit, while the others are relatively mild builds. 

Displacement: 211.67(212) vs 223.21(223/224) vs 228 vs 236.15(236) vs 240.11(240)

In every test, adding displacement has improved performance, especially low-speed torque. Increased displacement has many benefits, from increasing power while usually broadening the powerband and moving it down the rpm range for better acceleration to improving idle quality and drivability. 

The Wildcat 240RS has specs similar to the Tillotson 236R in terms of compression, displacement, etc. While the Wildcat 240 has a small advantage in size, the Tillotson 236 has a better rod and piston combination that helps improve rod ratio/angle, which appears to make a big difference in performance. 

We now have a 240cc Tillotson kit with a forged rod and piston with coated skirts. It will be interesting to see how that combination performs. 

Compression Ratio

There is a reasonable gap in compression. We have seen compression help, but it doesn't always mean the engine will make the most power. Regardless, the Predator 224, the small engine, has the highest compression ratio, around 12.5-12.64. The stage 4 head says the head has been milled .065" but doesn't give cc measurement; instead, it says it should result around 12.5:1, but checking with compression calculators, it could be as high as 12.64:1 with the .032 copper head gasket. 

Compression is good for power and primarily peak torque, but it can come at a cost, requiring higher octane or possibly damaging your engine. Red Beard had to rebuild the Predator 224 because the bore cracked, and the sleeve was trying to come out. Usually, block failure can occur for this reason, and many blame the quality of their blocks, but rarely do they calculate their compression. We also need to consider dynamic compression, which has as much impact on octane and requires more than static compression. Again, most do not measure their compression, which leads to engine or parts failures. It's reasonable to say the Tillotson 236, while only around .25hp less than the stage 4 224, will be more reliable because it's not relying on compression to get there. 

Peak torque can be improved by stroke/displacement or compression; given the choice, stroke/displacement has more benefits and is more reliable. 

Cylinder Head: Predator 212 27/25 Hemi, Aftermarket 27/25 Non-Hemi, Wildcat WC946 31/25 Non-Hemi. 

The Predator 212 and Predator 224 use modified versions of factory heads, whereas the WC946 is a head redesigned based on the factory heads. We don't have flow numbers on the Predator'sPredator's heads, but when we compare the ported Wildcat 27/25 Hemi Head, the WC946 will flow at .250, while the Hemi head flows at .400, which is mostly due to the valve size. That means we can get by with less camshaft to make similar power. What it takes for a ported Predator 27/25 hemi head to compete is about 10 degrees more duration on the camshaft and about 40% more lift at the valve. To make that happen requires a lot of work. The same is true of the built Stage 4 head used on the Predator 224, which has a larger 28.5mm intake valve, comes with spring pockets cut for, and is assembled with stiffer dual valve springs.

We have explained to many customers the problem with installing more aggressive camshafts with more lift is the amount of work and cost to stabilize the valve train from bigger springs, which require cutting pockets, roller rockers, and cutting push rods. All require more clearance checks to prevent issues. By increasing displacement and the performance of the cylinder head, you can increase performance without going beyond the stock or mildly modified valve train. Regarding performance, the head is one of the most significant upgrades that make your other upgrades work. In many cases, guys can change carburetors and cams and see little change in performance. A good cylinder head can achieve better performance with milder modifications and components than a bad head with the best modifications and components. 

Rocker Arms: Stock Non-Hemi vs. 1.2 Steel Hemi Rocker vs. 1.2 Gage Billet Non-Hemi Roller Rockers. 

Rocker arms improve power by increasing the cam's lift, which is a 1.2 ratio or 20%. Rocker geometry significantly affects valve motion and harmonics, affecting performance. So, while you should be getting 20% across the cams's lift points, it may or may not depend on the installation. However, there always seems to be some improvement. These aftermarket rockers claim to stabilize the valve train due to the shaft mount, reduce deflection, and reduce friction because of the bushings and roller tips. We haven't done back-to-back testing yet to confirm. Still, if it's all true, the Wildcat and Tillotson using stock rockers would be at a disadvantage, but these engines are still making similar power due to other advantages in the engine's design. 

The consequence of aftermarket rockers is primarily added weight. The valve springs must control the valve train, so increasing the weight of the springs, retainers, rockers, push rods, and lifters can add up and require more spring pressure to prevent valve float. All engines can turn over 8000rpms, but the Wildcat and Tillotson do so with 26-lb springs and a stock valve train. 

Carburetors: WC22 (26mm)Round Slide vs TM24 Mikuni Flat Slide

Carburetors can be a matter of contention for some. Many do not like the Knock-Off VM22 style carburetors, and for a good reason: most are difficult to tune, and most returned carburetors do not work well either. Those bad experiences led them to start with a more expensive flat-slide carburetor. 

We redesigned the WC22 and continue to improve the carburetor's performance because of the low cost, popularity, and the ability to mount it more securely and closer to the engine. 

Most would say a flat slide carburetor is a better-tuned and better-performed carburetor. We agree. If we blueprinted a round and flat slide, the flat slide would be better. Even a flat slide that is 2mm smaller will flow almost the same and still outperform a round slide carburetor. However, it comes down to tuning, and our tests are evidence of this. The 236 engine has bigger valves but doesn't have as much cam, rocker ratio, or compression as the Predator 224. It makes more torque and only .25hp less horsepower. Our WC22 is holding its own against the original Mikuni TM24 carburetor. Most importantly, if you still think the WC22 is holding the engine back, we recommend our PWK24 for more performance. 

While we stroked the 228R to 236cc, you can buy the 236 or even a 240cc Tillotson and build it from the ground up with the cam, head, and carburetor you prefer to run. That said, the stroked Tillotson would easily make more power than the Predator 224 with a flat slide carburetor, and the cost would still be less than the Predator 224 stage 4 build. 

Camshaft: Banzai 265 vs Fire265 vs CL-308

The 228R and our stage 3 kit are running our Banzai 265 camshafts. 265 cams are very popular because they increase performance without needing valve train modifications and are half the cost of bigger camshafts. The Fire 265 cam is $100 and has 10 degrees more duration. Generally, more duration will move the powerband to a higher rpm; depending on the centerlines, it can broaden or narrow the power band. For example, the Banzai typically peaks around 6400-6600rpms with most 212-225cc engines, even when the head gets ported. However, the 228R made peak power at 6700rpms and the 236R at 7000rpms. It seems the rod and piston design is improving top-end performance. The Predator 224 has to have more duration and lift to make similar peak power, but because the 236 is a bigger engine with less duration, the torque is higher even though the 224 has more static compression. 

The Predator 212 has the Cl-308 with 1.2 ratio rockers for about .370 total lift. The Predator 212, or when it was stroked to 223cc, making it the same as the Predator 224, the combination of head, cam, and rockers only produced around 18hp. While that is still very good, it is about what it takes to get there, and that is much more valve lift. It's about 40% more than the Wildcat 240 and Tillotson setups and 16.5% more than the Predator 224 Stage 4 Head. We said the ported WC946 cfm at .250 lift is about the same as the ported Wildcat 223 Hemi at .400 lift, and we believe the Predator 212 would be no different. That means more camshaft is required to make up the difference in flow. 

When building an engine, we recommend starting with a head and the engine platform and working backward to meet your goals. That was our thought process with the 228R-MKII and Wildcat 240.

Flywheels SK201 vs. ARC Flywheel

There are a few differences between the flywheels, and many ask which one performs better; it's hard to say through our test which flywheel is truly better, but we can look at the specs of the flywheels that may be a better choice for your combination. 

Ignition Timing: The ARC is 32°, which you may see on most cam cards, but that doesn't mean you are getting the best performance for your combination. For the Predator 224, 32° may be all it needs or possibly less because of the engine's compression ratio. We have found 34-36° work best for most combinations on gas. One drawback would be kickback during kickstart. The more timing you have, especially with higher compression ratios, is kickback when you pull start the engine, so you may need to compromise some torque to make the engine easier to pull start. 

The Wildcat 240RS dyno testing has shown that ignition timing has the biggest impact around peak torque, which you are tuning when setting your ignition timing. While it can help some with peak power, its significance is peak torque. In other words, your engine may still make good horsepower if you need to back off the timing to make it easier to pull start. 

Weight—The ARC weighs 3.35 lbs, and the SK201 weighs 2.79 lbs, which is a small difference, but the goal of reducing weight is to use less power to accelerate the flywheel so that that power can be used on your kart or minibike. It would be difficult to test on the dyno, but it should help with engine response from a dig or low speed when on and off the throttle. 

Spark Plug Autolite AR3910X Vs NGK BPR6ES vs Torch K7RTI

Autolite 3910X – This plug is the coldest heat range for Autolite plugs and is designed for endurance or boosted applications. In our application, the plug is too cold and may not burn the carbon off the plug, which can mislead some in their carburetor tuning. It has been frequently used in karting because the tip decreases the chamber volume to increase compression. Many can attest to the spark plug making more power on the dyno. However, if the carbon builds up, it can cost performance, which means it requires frequent replacement to maintain the advantage or, at minimum, prevent a loss in performance. 

NGK BPR6ES—The BPR6ES is within one heat range of most stock plugs. Essentially, it's a stock replacement plug for most engines, so increasing performance isn't expected, but it's hard to argue with the quality and consistency of an NGK brand plug. 

Torch Fine Wire K7RTI – Torch is not immediately associated with performance, but many don't understand the aspect of the plug's design that improves performance, brand aside. The fine-wire iridium plugs have consistently picked up .2-.3 horsepower over the NGK BPR6ES. If you are brand conscious, you can buy NGK, Bosch, etc, that make fine-wire iridium plugs. We recommend getting a plug-1 range colder than stock for these engines. The fine wire is the key for the spark to be more concentrated and consistent. Typically, the air-fuel ratios are most consistent, which means tuning will be more consistent, and the engine will be more efficient. 

Block: Tillotson R-Series vs. Wildcat Block Predator/Ducar Block

Since the introduction of the Tillotson R-Series block, it has been considered to be the best clone block on the market, which helped elevate the clone to be on par with the Briggs Animal and World Formula. Due to its perceived superiority, it was banned in some of the 196cc box stock classes. 

It's not argued that the Tillotson is the preferred block for high-performance builds and racing applications today. 

The Wildcat 223 and 240 blocks were alternatives with reinforcements on the jug, which helped improve the blocks' strength and durability far beyond the Predator 212 and a step above the Ducar-based blocks, which have the reinforcement on the top of the jug but not the bottom. 

The advantage of the Tillotson and Wildcat is their 72mm bores. Sleeving a Predator or Ducar block costs more than buying a Tillotson block and will still not be as strong. For that reason, the Tillotson is the preferred block. 

The Predator 224 Stage 4's4's compression ratio is beyond the safe limit on pump gas for any block, but the Predator/Ducar block doesn't help the situation. Red Beard had to rebuild the Predator 224, but luckily, he caught it in time to prevent a total engine loss. 

Again, we want to bring to your attention that the Wildcat 240 and the Tillotson 228R/236R are not pushed as hard to make similar power, making them more reliable. 

Rotating Assembly: Crankshafts, Rod Length and Pistons

Since we started working with Red Beard with the Road to Horsepower, we've not passed our "stage 3" level builds, which are the WC22 Carburetor, 265 cams, billet rod, and billet flywheel. We can compare the differences in the engine platforms and see how this combination of parts can make power. We've mostly compared heads and displacements, but more is not visible, such as piston design, ring thickness, rod-stroke ratio, and rod angle. 

For example, the bigger displacement engine usually makes the most power and torque. While this is a significant element of the engine's design, the 228R and 236R have similar or better power than the Wildcat 240RS. The question is, why?

The Wildcat 240RS still uses a factory-style piston with long skirts, thick piston rings, and a large wrist pin journal and compression height. The Tillotson 72mm piston reduces friction with shorter, narrower skirts and thinner, low-tension rings. The wrist pin is small, and the compression height is shorter to allow longer rods, changing the rod ratio and angle. The piston is also much lighter. 

Obviously, friction is not good. Friction causes drag, which means power is wasted to overcome those losses. It can also increase heat and wear, further reducing the engine's performance and longevity. 

Weight is a huge factor in changing engine performance. When we think of piston weight, we may think of rpm durability or rotating assembly balance, but most only think of these things very generally. There is more significance when we think of our single-cylinder, industrial-based engines. Balancing a single-cylinder engine is not completely possible without a balance shaft to balance the assembly at 90 and 270 degrees of crank rotation. When weight is added to the crankshaft to balance the rotating assembly, it may improve balance around the top dead center and bottom dead center, but the secondary balance worsens. Usually, engine vibrations are worse at lower speeds. The heavier the pistons and crankshaft counter weights put more stress on the piston, crankshaft, crank bearings, and block. Reducing piston and rod weight will get closer to a "balanced" rotating assembly without worsening secondary vibrations in most cases. The engine will run smoother and wear less, and the blocks and side covers will also be less likely to crack and break. 

Another piston design feature is the compression height and wrist pin size. The smaller wrist pin reduces weight and allows a longer rod to be used. Before we explain the impact of rod ratio, here is a list of rod ratios from some of the engines that have been tested

Wildcat 240 3.303 Rod / 2.323 Stroke = 1.422

Tillotson 236R 3.415 Rod / 2.283 Stroke = 1.496

Tillotson 228R / 2.205 Stroke = 1.58

Wildcat 223 w/billet rod 3.353 Rod / 2.283 Stroke 1.469

Predator 224 3.305 Rod / 2.283 Stroke = 1.448

While the ratio is very similar, we want to show the differences and how rod ratio can influence engine performance. The rod ratio affects the piston speed of the engine at the top dead center and bottom dead center. The lower the rod ratio, the faster the piston moves at tdc and bdc; the higher the ratio, the slower it moves. The 1.422 ratio of the Wildcat 240 moves faster at tdc and bdc than the 228R 1.58 ratio. How does this affect engine performance? At the bottom dead center, it gives the exhaust more time to expel the exhaust during the blow-down phase. The fewer combustion gases left in the cylinder, the less resistance the piston has to back up, and the more clean volume is available to fill during induction. Also, it means you have more time to fill the cylinder during the intake phase at BDC. At TDC, the slower piston can give more time to expel any extra exhaust. However, if you have an early intake opening, it can increase reversion. The slower piston can also give more time for scavenging at higher rpms, which can help get air moving before filling the cylinder. During the engine's power phase, the piston moves slower at TDC during combustion, which can help increase cylinder pressures for more power.

The rod length will also change the dynamic compression of the engine. We often measure the static compression of these engines, but we haven't fully covered dynamic compression that is affected by cam timing, specifically the intake closing event and rod length. In other words, the same cam in two engines with different rod ratios will have different dynamic compressions. You must also consider how much the cylinder is being filled to know how much is being compressed. If you have a 236 but only 200cc is being filled, you are not compressing as much volume as you think, and the reason is that increasing static compression doesn't increase power as much as you think. If you go back to the Super Ghost video vs. the Wildcat 223, the Super Ghost has much less static compression but has similar power because the Super Ghost filled the cylinder better. Or suppose you are overfilling the cylinder like in a boosted application. In that case, you are compressing more than you think, which is why most boosted engines have lower static compression ratios. 

The other benefit is rod angle. As the rod ratio gets smaller, the rod angle increases. Depending on the angle's aggressiveness, it can lose its leverage on the crankshaft and increase stress on the piston's skirts. The crankshaft can increase pressure on the side skirts, especially on the thrust side of the piston, and will increase friction and wear, reducing performance and reliability. 

Horsepower and Torque:

We're looking at the power made by each engine with their ported heads. The Wildcat made 17.24hp at 6600rpms and may, to surprise by some, be the lowest in comparison. The engine also reached its peak hp the soonest, typical of larger displacement engines. However, the engine made 14.96ft-lbs, similar to the Predator 224's 15.01t-lbs, with only a .05ft-lbs difference, but the Wildcat made it 300rpms sooner. 

The 228R produced a little more horsepower than the Wildcat 240 but less torque. It also produced .35-1.15 more torque than the Predator 212/223 engines but .41- .56 less horsepower. The performance is pretty good considering the price is similar, but the 228R achieves greater numbers with less cam, rockers, and carburetor. 

As we said before, the Predator 224 is a fully built engine that is nearly maxed out and is probably past its limit regarding compression. The engine made the most horsepower by only .25hp and 100rpms higher than the Tillotson 236 engine. However, it doesn't make the most torque. The Tillotson 236 made the most torque because of its bigger displacement and superior rotating assembly. The Tillotson is only 1mm stroke or 4cc, different than the Wildcat. Still, the Tillotson's piston and our longer forged rod combination reduce friction and promote better cylinder filling, allowing it to make a little more torque and top-end power. 

Here are the power averages of each engine (hp + torque /2)

Tillotson 236R - 17.02 - Cost $1089.93

Predator 224 Stage 4 - 16.9 - Cost $1,399.63

Predator 223 - 16.28 - Cost $1,100

Tillotson 228R - 16.18 - Cost $899.99

Wildcat 240RS Stage 1 - 16.1 - Cost $799.98

Predator 212 - 15.8 - Cost $900

Conclusion:

Our goal is always to compare value or cost vs performance, and performance is more than peak power figures but where power is made, the engine's potential, and the components' durability and quality. Our goal is to make more powerless expensive with less work. The difference in power is minor between the Tillotson 236 and Predator 224, but the Predator 224 takes more work and money and is less reliable. The engine is beyond some limits where the 228/236 or 240cc engines are not under as much stress to make similar or superior power. Not to mention, very little of the Predator 224 remains where we haven't added anything to the 228R except for the 58mm crank and rod to make it 236cc. 

If you could track engines over the last decade or the last 4-5 years, there has been a significant gain in performance and durability. Just in the months we've been testing engines with Red Beard's garage, we've seen many 212 to 223 builds, which are only an 11-12cc difference, and how significant those engines were. Now, they are running 236-240cc, which is 13- 17cc more than the 223/224 engines. That means this increase in displacement is greater than the previous generation of engines. 

The 212 engines are still the most commonly built, but it takes so much more to make a similar horsepower, only to have far less torque. 

However, as much as we have gained, some insist on more. Many want pre-built engines with better carburetors, bigger cams, and more headwork, but the cost increases exponentially. We're not saying these packages make the most power, but they make very good power for the price. The best and most affordable route for maximum power is a scratch build using one of our bottom-end kits.