Field Report: Engine Block Design — Cast vs Billet.

What considerations go into taking a 150HP engine and making it produce 600HP with huge cylinder pressures, reliably?

When you want to double, triple or even octuple an engines output, at some stage you’re going to find the limitations of your factory block and head castings either in dramatic fashion or via constant repairs and rebuilds for ‘minor’ issues. In professional motorsport, either outcome is unacceptable.

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David Mountain of MounTune runs Andre though some of the block failures they have seen during their engine development programs where very high cylinder pressures are seen to produce large amounts of low-end torque for World RX competition engines where they are running 4 times the power the engine would produce in factory trim.

Discussed are the bore size, block weight, cylinder bore centers and other design parameters they must work within depending on class regulations, how they get away with the pressures a diesel engine would run in a steel block using aluminium instead, and some of the coatings they use on bore liners and piston rings to make it all work.

David also gives some great insight into cast vs billet block production including some of the advantages when it comes to casting. We also learn how 4 week to 3-month production lead times for modern 3D computer-aided design (CAD) production via software like SolidWorks compares to the 5-6 month days of 2D drawings. Interestingly, even with the use of finite element analysis (FEA) a lot of real-world experience is drawn on to ensure a balance is found between the many, many considerations and tradeoffs that every design tweak carries.

Lastly, we learn how MounTune avoids any issues with cylinder sleeves dropping, why the factory design for head studs is not optimal once you start running higher pressures, Nikasil coating use and how before any tools have been lifted the CAD process can be used to ensure those regulation weight targets are hit along with avoiding any major design flaws. While some of this technology seems like magic that does the work for you, in reality without that real-world experience and knowledge bank to draw on it’s useless. Just like any quality tool, the person in charge needs to know what they’re doing to get the desired results.