Project Nissan 350Z - Sport Compact Car Magazine

All Motor Nissan Vq35de Cnc Valve Seat Cutting Machine

After CNC-machining, each valve seat is re-cut to fit larger valves. This CNC valve seat cutting machine uses a pre-programmed cutting path to create the four or more angles and transitional radii in each valve seat with just one cutter, unlike older-style machines that require a different cutter for each valve angle.

After CNC-machining, each valve seat is re-cut to fit larger valves. This CNC valve seat c

However, just because our pistons are one-offs, that doesn't mean they're better. Cosworth engineers altered the design of certain parts going into our Castrol Syntec Top Shop Challenge VQ35DE to give it an extra competitive edge, given the nature and rules of the competition. Of course, the trade-offs with lighter, thinner parts are strength and durability; shorter piston skirts are more prone to more piston wobble and wear over time. If this VQ had been going into our Project Z, we'd opt for more durable off-the-shelf parts.

Our Cosworth-forged H-beam rods also feature a bag of tricks only seen from top-end rod manufacturers. Again, nothing secret, just meticulous and costly machining that takes unnecessary material and weight from around the rod bolts and journal, even lightening the pockets in the rod arm itself. Cosworth opted to leave out oil-slinger notches on the rod journals to avoid additional stress risers.

Witnessing Cosworth's assembly process is humbling. Once again, no secrets; just years of experience and meticulousness. The billet crank is bolted with the deburred stock girdle using Cosworth hardware. Bearings (also Cosworth) are lubed with oil applied by brush instead of being dripped on. From the top, each bore is re-measured, down to the ten-thousandths, and compared to which piston fits which bore best, per design tolerances. Each rod is prepped and readied in a custom-built clamp jig just for this purpose. Ring gaps are measured inside the cylinder and ground to spec if necessary before each piston is dropped in with custom tools from the machine shop. The entire process is immaculately clean.

The finished valve seat (right) compared to the OEM valve job is significantly different. The CNC valve seat machining is so precise that lapping each valve is no longer needed.
The finished valve seat (right) compared to the OEM valve job is significantly different.
Assembly of the valvetrain is performed on a special jig with adaptor plates for the various Cosworth heads. This plate is for a Subaru head. The jig allows one head assembly technician to assemble the valve, valvespring, retainer and keeper in one swift motion. The jig is actuated by a foot lever and frees up both hands to insert the keepers.
Assembly of the valvetrain is performed on a special jig with adaptor plates for the vario

Much of the top end will be built with parts already available to the public, including pre-assembled Cosworth CNC heads and head gaskets. The CNC heads are one of Cosworth's most highly touted products, offering precise and consistent head porting, 1mm larger stainless steel intake and Inconel exhaust valves, plus an upgraded, lightened valvetrain. The head starts off as a brand-new casting, purchased from Nissan, ported by a multi-axis CNC machine programmed to take out exactly the same material from each port.

Cosworth has been able to improve upon the already amazing stock Nissan head through repeated flow-bench testing of the port and valve seat geometry, increasing intake flow at maximum lift by 19 percent and exhaust flow by 22 percent. Flow gains are linear throughout the range of valve lifts, with only minor losses just as the valve opens. Our CNC heads will be fitted with development cams, which we'll talk about next time as we go through the final touches, with intake and exhaust manifolds, cam development and tuning-all done on Cosworth's in-house engine dyno.