Project Do It All S13, Assembling the Bulletproof SR20DET Bottom End!

The K1 crank is machined from a 4340-high nickel and molybdenum steel forging. 4340 is known for its strength, toughness, and impact resistance making it ideal for crankshafts.  The crank is post-machining heat-treated for durability.

The crank has cut down counterweights for less weight and less windage loss.  The machining on the crank is beautiful.

Even with a 6mm stroke over stock the beefy SR20 crank design still has strong jornal overlap.  This crank isn’t breaking anytime soon!

The crank journals have a really nice finish and generous fillets for strength and fatigue resistance.  The oil holes are chamfered.

In addition to heat treating, the crank has been aggressively shot peened after machining, this greatly improves fatigue strength.  To further increase the crank’s strength, durability, and wear resistance, and to reduce friction, the crank was cryo-treated by CTP Cryogenics and then WPC-treated.  Although the crank is pretty well balanced from K1, we also had our crank high-speed precision balanced to less than a gram of imbalance.

The K1 crank has screw-in oil passage plugs instead of your typical pressed-in balls.  Not only is this more positive but they can also be easily removed for cleaning.


  1. What are the boundary conditions for the FEA images? Something looks a little strange in how forces are applied to the little and big end… Are they not treating it as a pinned connection with bearing loads for the application of the loads?

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