Join us as we take a closer look at the McLaren engine OE sleeve design, explore its evolution, and reveal the key improvements we’ve incorporated into our CSO-spec sleeve. All this and more in today’s episode of Engines 101.
Light weight was a priority for development of these McLaren engines. This focus is evident in the design and evolution of the OE sleeve. Let’s start with the first sleeve introduced in the M838T.
This sleeve was a simple straight-wall design made from aluminum. Inside the bore, a thin layer of Nikasil was electroplated to provide a durable surface for the piston rings to ride on. The sleeve was inserted into the block from the top, with the flange serving as the primary locator—sandwiched between the block and the head. The bottom of the sleeve was a slip fit into the block, sealed with two O-rings to keep coolant out of the crankcase.
While this design was exceptionally lightweight and well-suited for the lower power output of the early cars, it revealed its limitations under higher stresses. A sleeve experiences significant side loading during the power stroke. As the piston is forced downward by combustion it is also being pushed sideways due to the angle of the connecting rod. The lack of support at the bottom of the sleeve allowed it to flex, which, over time, weakened and even cracked the sleeve. Here, you can see evidence of the sleeve rubbing against the block due to this movement.
To address these issues, a new sleeve was introduced with the M804T McLaren engine. Designed to handle the increased side loading from the stroker crankshaft, this sleeve was made from iron, a much stronger material than aluminum. However, this came with a tradeoff: added weight. To mitigate this, material was strategically removed wherever possible.
The new iron sleeve also featured a significant design improvement at the bottom: it went from a slip fit to a press fit, providing much better support. While this new sleeve was a major upgrade over the original, it wasn’t without its challenges. Under the extreme loads generated by big-turbo or tuned cars, even the iron sleeve would distort slightly, going out of round and developing a measurable barrel shape. Here, you can see how even the iron sleeve exhibited some movement and wear against the block at its base.
For the CSO sleeve, we took the best qualities of the OE designs and made strategic improvements to push performance to the next level. Here’s what sets our sleeve apart:
- Material: We selected high-grade ductile iron for its superior strength and durability.
- Bottom Support: To eliminate movement at the base, we removed the undercut, more than tripling the contact area with the block for added support.
- Wall Thickness: To combat distortion and barreling in the middle of the sleeve, we increased the wall thickness by over 50%.
- Cooling Efficiency: We incorporated the factory cooling groove in the flange, and to enhance cooling, we added ribbing in the water jacket, increasing the contact area with the coolant.
The result? The ultimate engine sleeve for McLaren enthusiasts looking to maximize performance and reliability. To learn more check out our Engine Program page!