Project STurdteen: Building the SR20DET Engine

To assure good head seal even with boost and drifting abuse, we used a JE Pro Seal head gasket.  The Pro Seal gasket is an MLS type gasket which uses multiple layers of thin stainless steel which are polymer coated to form a tough and forgiving seal to the block.  A folded stopper layer is used around the cylinders to give increased clamp load to further improve the seal.  The folded stopper really helps on boosted engines.

Since oil control is critical in a boosted engine we installed an Ishiwata-Johnson crank scraper and windage tray.  This piece is the scraper which wipes oil from the crank and helps strip the windage cloud away from the rotating crank and rods.  It aids in oil return to the pan, reduces oil aeration and oil temperature.  It also frees up a few horsepower.  More oil in the pan and less twisting around the spinning crack getting frothed up and increasing friction is a good thing.

This part is the windage tray, it also helps strip the cloud of oil off the crank, helps deaerate it and returns it to the sump quickly.  These parts reduce entrapped air in the oil which makes a huge difference in bearing load capacity, reduce oil consumption, reduce friction, increase power and lower oil temperature.

We used ARP studs for the main caps and cylinder heads.  The studs replace the stock torque to yield bolts and allow higher torque for increased clamp loads and do not stretch out of shape with each torque down like stock. ARP studs are made of 8740 chromoly steel. 8740 has superior strength over a more common chromoly like 4130 because it has a higher carbon content and responds to heat treatment better.  It also makes use of nickel as an alloying element which increases toughness.  8740 has a very high tensile strength of around 200,000 PSI. The ARP studs and bolts also have several design features like rolled (superior to cut threads due to good grain formation in the thread root) asymmetrical J-form threads with more engagement area on the stressed side and a reduced center diameter to reduce stress risers. ARP studs and bolts, when applicable, also have high quality forged nuts and precision ground and hardened washers for accurate torque and positive retention.

Howard started to assemble the engine by hanging the pistons on the rods and putting the rings on the pistons. The rod bolts were lubricated with assembly lube to assure accurate torque readings.


  1. For competition engines, I prefer not to use them because they are torque to yield and they stretch and take a set. They can only be reused maybe once and it’s a good idea to change them every time on a serious engine.

  2. for the mains, did you guys use arp’s torque spec or something else? I always thought it was a bit high

  3. Are you modifying the upper oil pan to clear the windage tray or did you find/make a spacer? the jet nuts on my tray touch the upper pan and require me to mod my pan.

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