Inside the Cosworth VQ35DE Rev-Up! Part 1


To improve our engine cooling we changed our engine's water flow pattern from the stock front to rear to the front to rear up and down flow path of the later VQ35HR.  This provides much better cooling.  To convert to the HR's water flow pattern we have to use the HR head gasket and enlarge this water passage in the block to the HR's dimensions.
Cosworth's block is machining perfection.  All edges are deburred, the block deck, crank bore and cylinder bores are all squared up and the bores WPC treated.  Finally the block is once again ultrasonically cleaned to perfection and ready to assemble.

To secure the main caps and cap girdle we used ARP studs.  We chose ARP studs over the stock torque to yield bolts because studs are easier on the block threads and the caps and girdle are held in better alignment.  Studs also provide more accurate torque readings because they don't twist into the block when being tightened. 

ARP studs are made of 8740 chrome moly steel. 8740 has superior strength over a more common chrome moly 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 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 also have high quality forged nuts and precision ground and hardened washers for accurate torque and positive retention.

Here is a close up of the double parallel ground ARP washers.  The washers are hard and absolutely flat.  This ensures accurate torque and good retention of torque after tightening.
VQ engines are known to lose dangerous amounts of oil pressure during hard cornering resulting in bearing failure so we installed Cosworth's one way baffle in the oil pan.  This allows oil to flow in only one direction helping keep oil in the sump around the pick ups.  These flaps are designed to only open in one direction.  
Here is the view that the oil sees going toward the sump, the flaps deflect and allow the oil to enter the sump.


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