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EC 236RX 4-Cycle Racing Engine Bottom End Kit
Complete Exploded View of the EC 236RX Short block
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EC 236RX 4-Cycle Racing Engine Bottom End Kit

Part Number: 236RX-KIT
Online Price: $509.99
EC's Tillotson 236cc/14.41ci Short Block Kit
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Description

EC 236RX 4-Cycle Racing Engine Bottom End Kit – Updated Performance and Value


The updated EC 236RX Racing Engine Kit is engineered to build a high-performance kart or mini bike racing engine that delivers exceptional power and reliability at an affordable price point.


From the outset of our Tillotson Engine Program development, we focused on creating a build capable of handling the demands of a 14.5ci Open Modified class. The 236RX delivers 236.15cc (14.41ci) of displacement, putting you right at the competitive edge while remaining budget-friendly. This kit provides a partial short block designed to integrate your existing clone or Predator parts, racing carburetors, and other components. For those building a brand-new engine, we offer a range of add-ons to complete your setup. Please note, the engine and short block come unassembled for flexibility.


Key Components:

EC 72mm Forged Flat Top Piston
Our new forged 72mm piston replaces the standard hypereutectic Tillotson piston to significantly reduce weight while improving strength.

  • Weight: 122g (vs. Tillotson’s 131g)
  • Features moly-coated skirts to reduce friction and wear
  • Shorter wrist pin height allows for a longer connecting rod

Available oversizes include:

  • 72.1mm (2.8385”) – 236.8cc (14.45ci) – Legal for 14.5ci Open Classes
  • 72.25mm (2.8444”) – 237.79cc (14.51ci)
  • 72.50mm (2.8354”) – 239.44cc (14.61ci)
  • 72.75mm (2.8641”) – 241.09cc (14.71ci)


EC Forged Billet Connecting Rod
This longer 7075 aluminum forged rod is designed to achieve zero deck height with the new piston. The realigned grain structure provides superior strength compared to billet or cast rods. Rods are anodized for corrosion resistance and aesthetic appeal.


72mm Tillotson Reinforced Block
The core of the engine, this block is thickened and reinforced to minimize flex and distortion, reducing power loss from crank flex and blow-by. Originally designed for endurance racing in the Tillotson 225RS/T4 class, it features one of the largest factory bores at 72mm—ideal for high horsepower applications.


58mm (2.283") Stock Stroker Crankshaft
Our exclusive 58mm crankshaft offers a stroke just 0.017” less than aftermarket billet cranks but at a fraction of the price. This crank allows you to build a competitive short block without the premium billet crank cost.


Kit Includes:

  • Tillotson 72mm Reinforced Block
  • EC 72mm Lightweight Forged Piston
  • EC Forged Connecting Rod
  • 58mm Stroker Crankshaft (EC Exclusive)
  • Stock Sidecover
  • All necessary hardware and gaskets for short block assembly

Pushrods are not included; we recommend chromoly pushrods for all builds.


Additional Recommendations & Options:

  • Upgrade to our billet side cover for enhanced crankshaft stabilization and block stiffness, especially if pursuing high horsepower builds.
  • Explore our evolving lineup of cylinder heads, camshafts, and carburetors designed to maximize your 236cc engine’s power potential.
  • Customize your engine with various blower housing colors and recoil starters, with included kill switches.


Important Notes:

This 236RX Engine Kit is a dedicated racing product, intended for experienced builders. The final assembly and tuning are the responsibility of the builder. Due to the nature of this product, we do not offer any warranty.

If you need assistance with component selection or engine setup, feel free to ask questions on this page or contact us directly by phone or email.

FAQ

Frequently Asked Questions (FAQ):

Q1: Does the kit require any machining or clearance-ing?
No, the components included in the kit do not require additional machining or clearance. However, some camshafts may need clearance for the compression release or lobes. If using a copper head gasket, it's recommended to have the cylinder head o-ringed for adequate cylinder sealing.


Q2: Do you assemble the 236RX?
No, the 236RX kit comes unassembled to allow for customization. It can be completed with various camshafts, flywheels, and cylinder heads that may require additional clearancing. Assembling the kit yourself keeps costs down and allows for tailored performance.


Q3: How much horsepower can this kit produce?
While specific horsepower figures can vary based on components and tuning, high-performance factory engines from the 60s/70s produced about 1hp per cubic inch. At 14.41ci, that's approximately 14.4hp. Pro Stock engines of the same era produced about 2hp per cubic inch, equating to around 28.8hp. However, achieving these figures in an air-cooled, power equipment engine with limited technology is challenging.


Q4: Is there a warranty on this engine kit?
The 236RX Engine Kit is considered a racing product, and the final assembly is the builder's responsibility. We do not offer any warranty for this engine package.

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