EC Stroker Kits: How to measure your deck height?

Video Credit to Red Beard's Garage

"There is no replacement for displacement." 

One of the reasons the 212cc engines like Predator became successful was its extra 2mm bigger bore and 1mm more stroke over the 196cc engines. About 7-8 years after the release of the 212, the 223/224cc engines hit the scene, offering a 58mm crankshaft, which is 4mm more than the 196 and 3mm more than the 212. If you have watched the previous videos comparing the Wildcat 223 and Tillotson 212E, which include comparisons of other engines, you know the bigger displacement engines have advantages in torque and horsepower. 

The bigger displacement engines make better engines for racing and recreational builds by improving torque at lower RPMs for cruising and trail riding. 

Suppose you have an engine without a 58mm crankshaft; you are still in luck. We offer stroker kits to make most 212 engines into a 223, or if you have a Tillotson 72mm bore block, you could go from a 225 to a 236. 

223H-SKA is for the Hemi 212 Predators

223E-SKA is for the Tillotson 212E, Ducar 212 and Ghost 212 Engines

236-SKA is for the Tillotson 225R 72mm block to make 236cc

263-SKA is the rotating assembly used in EC's 76mm Bore Tillotson Blocks to make 263cc engines

58mm Crankshafts: How does a 58mm stroke crankshaft improve performance?

Displacement: The displacement of an engine is based on the bore and stroke of your engine. The 58mm stroke crankshaft increases the engine's displacement; a bigger engine will have more capacity for more power potential. 

Compression: The engine's compression ratio is the total volume of the engine displacement plus the combustion chamber when the piston is at the bottom dead center divided by the combustion chamber volume when the piston is at the top dead center. Many things can affect the compression ratio of the engine. Keeping all the specs the same but increasing the engine's displacement will increase the compression, too. 

Piston Speed: When we think of piston speed, we often associate it with the engine's RPMs, which is only part of the equation. Increasing the stroke will increase the piston speed of the engine, which is the speed at which the piston travels up and down the bore. You can look at this two ways: an engine with a 58mm crankshaft piston will move faster than an engine with a 55mm or 54mm crankshaft at the same rpm or the same piston speed at a lower rpm. The higher the piston speed, the greater the potential depression or negative vacuum created by the engine. The greater the pressure differential, the more air will be drawn into the cylinder. You'll often see peak torque and power happen earlier in the rpm range, and you'll be able to better utilize bigger valves and bigger ports without losing velocity because the engine behaves as if the engine is turning faster. 

Mechanical Leverage: If you use a breaker bar, the longer the bar, the more torque you can produce. The same is true in your engine. The cylinder pressure pushing the piston down exerts more leverage on the crankshaft to produce more torque. 

Horsepower is a calculation of torque, torque x rpms / 5252 = horsepower. 

What pistons have EC Carburetors designed, and what do they use in their kits?

- 72mm Tillotson Hypereutectic Piston

EC Carburetors designed the 72mm Piston for the Tillotson 225RS engine and used that same piston in their 228R and 236R engine kits. The piston is a hypereutectic casting but is often mislabeled as a forged piston. Initially, the plan was to have the piston forged, but having it cast was less expensive and would still exceed the requirements of the 225RS engine. The lightweight design and short compression height allow a long rod to reduce lateral vibrations. The piston has been used in many engines, turning over 10,000.

- 76mm EC Hypereutectic Piston

EC also designed its own hypereutectic 76mm(2.99") piston, similar to the Tilltoson but with a longer wrist pin for added strength and a shorter compression height than the 72mm to allow a longer rod. Even though the piston is 8mm larger in diameter than the stock 196cc piston, the 76mm Piston assembly(piston, rings, wrist pin & clips) weighs 7+ grams less. 

- 72mm EC Forged Piston & Oversizes

While there has been huge success with the 72mm hypereutectic pistons, some racers have difficulty trusting anything but a forged or billet piston for their high rpms builds. EC also had the dilemma of not having oversized pistons to offer rebuilds. To fix both problems simultaneously, they made 72mm forged pistons with oversizing available. They shortened the compression height and had the skirts moly-coated to offer even more performance and value. 

- 70mm Wildcat Piston

The 70mm piston in the Wildcat is a factory 70mm flat-top piston, but it is slightly lighter than the flat-top piston in the Predator 212 Hemi and has less material underneath the wrist pin to offer more clearance. The extra clearance is essential for engines like the Predator 212 Hemi to use a 58mm crankshaft and not hit the counterweights when the piston is at the bottom dead center. 

What Connecting Rods have EC Carburetors designed?

- Tillotson Rod & EC Pinnacle Rod

We started designing rods when working on the Tillotson 225RS, where they created the piston and the connecting rod for that engine. 

Since they designed the piston, they could quickly design rods with different crankshaft strokes to be the first to offer 228cc and 236cc versions of the Tillotson engines. 

They also built rods for their other engines, including the Tillotson 212R and Wildcat 223. When people wanted to stroke their 212cc engines, we made rods to fit that crankshaft with the Wildcat Flat top Piston to maximize the extra displacement and increase compression.

Our design addresses many clearance issues when using the 58mm stroke crankshafts, such as the dipper and rod bolts, which normally hit the camshaft core, lobes, or block. 

We also made a rod for the Wildcat 460 and are developing many other Big Block and V-Twin Rods.

- Forge vs Billet

Many people are unaware of the differences between forging and billet, and many ask how they compare in strength, durability, and handling rpms. EC's small block rods are made from forging. A forging is a piece of billet that has been pressed in a die to a near-finished shape to realign the grain structure for better strength and durability. Any component made of the same material will be stronger as a forging because of the realignment of the grain structure. 

- Forced Oil Hole Dipper

One frequently asked question is related to the absence of the force oil hole dipper. The forced oil hole is omitted to prevent stress fracturing at higher rpms. In the history of small engine or go-kart racing billet rods, Clements, Burris, Lunati(same as the automotive brand), Briggs(World Formula), etc, do not use a forced oil hole dipper and have not had oiling issues. Even ARC has rods, for example, ones for the Briggs Animal, that don't have oil hole dippers. Those rods were designed with enduro kart racing engines that operate around 9000rpms or sometimes higher at speeds over 100mph and don't have a forced oil hole dipper. 

Are the rotating assemblies balanced?

No. Single-cylinder engines can't be balanced fully, and it's mostly due to the lateral forces created by counterweight at 90° and 270° of crankshaft rotation since there isn't the weight of the piston or another counterweight to cancel it out. Adding weight to "balance" the crankshaft may worsen these lateral forces. 

Single-cylinder dirt bike and motorcycle engines usually have full-circle counterweights and a balance shaft or gear to help reduce lateral vibrations. They also use very lightweight pistons and long rods for a higher rod ratio. 

Crankshaft balancing is a bit of dark art that requires technical knowledge, real-world experience, and the right equipment and technique for making correct modifications. For example, the rule of thumb is a 50% balance factor for general-purpose or moderate-performance applications. The balance factor is 50% of the reciprocating weight. However, high-rpm racing applications could have a much higher balance factor. How much balance do you need for your application? There isn't a one-size-fits-all percentage. There are many factors outside the weight of the components that can influence the balance or smoothness of the engine, such as the dynamics made during each stroke of the engine(intake, compression, combustion, exhaust), engine load, crankshaft/engine distortion, rod ratio, windage/splash lubrication, etc. 

Be very careful if you decide to have your crankshaft "balanced." Do your research and ask a lot of questions. 

How to measure the compression height of pistons and deck height of the block

To figure out your engine's deck height, you can measure your rotating assembly components; here's how:

1. Measure the piston depth when the piston is at the top dead center. Using our depth gauge, lay it across the bore of the block so that the point is on the top of the piston on the wrist pin centerline. Ideally, the center of the piston, but since the Ghost 212 is a dish piston, you need to measure it from the edge, and you can do this on both sides of the wrist pin centerline because most blocks are not squared.

Let's say the piston is .012 in the hole.

2. The crankshaft's stroke is 55mm or 2.165"; you can get a more accurate measurement by measuring the piston's travel from the top dead center to the bottom dead center. Take that number and divide it in half, 2.165/2 = 1.0825 or 1.083

3. Next, you need to measure the piston's compression height. Most kart/mini bike retailers, including those on Amazon and eBay, do not take this measurement correctly. Most measurements are taken from the top of the wrist pin journal to the top of the piston only, but they are supposed to be taken from the centerline of the wrist pin to the top of the piston. To do it correctly, measure the wrist pin journal and divide it in half, which should be .716" in the Ghost, .716/2 = .358. Add it to the measure from the top of the wrist pin journal to the piston's crown to equal .924 total.

5. Rod length should be 3.308 for that engine, but you can measure it by measuring the big end and small end journals and dividing those in half 1.180/2 = .59 and .716/2 = .358, adding the length from the top of the big end to the bottom of the small end, then adding all three numbers together should equal around 3.308

Add all the numbers together, .012(add if the number is negative or in the hole, subtract if there is piston pop-up) + 1.083(crank) + 0.924(piston) + 3.308(Rod) = 5.327 is the deck height of the Ghost 212. 

The stroker kit should fit very close to zero deck height; blocks may vary, so measuring your deck height before assembling your rotating assembly is important. You should be able to take any crank and piston and figure out their rod length to get zero decks or any piston depth they want.

Clearance for the 58mm Stroke Crankshafts

1. Use a 223/224 cam core. EC is working on updating their camshaft cores, which will allow the cams to drop in, so clearance doesn't need to be made for the compression release. Depending doesn't lift, duration, and profile of the camshaft, the camshaft may still need clearance for the lobe.

2. Remove the compression release from the camshaft or use a billet cam without a compression release. If you are racing and not required to pull start the engine, then removing the compression release allows the cam to fit without clearance, and there is no risk of the compression release failing since it's no longer on the cam.

3. Pre-clearance crankshaft. If you plan on stroking your engine but don't want to buy another camshaft, you can buy a pre-clearance crankshaft that will minimize effort and clearance to fit your camshaft.

4. Clear the crankshaft. EC has a blog showing two different styles of compression releases and the modifications needed for them and the crankshafts. They also show how to clear the camshaft's lobes using a big cam. https://www.eccarburetors.com/clearance-wildcat-predator-58mm-crankshaft