Build Series: Old School Labs-SR20VE/SR20DET Hybrid Engine Build, Part 3
After a bit of a break, we are back with our continuation of our SR20VE/SR20DET hybrid engine build up. In the second section of our series, we gave an overview into the project and certain key points of the engine block. In this installment, we are going to outline the key points with the cylinder head, cooling, and electronics as the final stage before we fire up this monster and begin tuning for maximum reliability and horsepower.
By now, you might be asking yourself, why go through the trouble and extra costs of mating a SR20VE cylinder head to a SR20DET cylinder block? The answers are pretty compelling.
For starters, the Nissan Ecology Oriented Variable Valve Lift—otherwise known as NEO VVL—is a variable valve timing and lift head. The VVL system varies lift and duration by using hydraulic pressure to switch between two different cam lobes similar to how the Honda VTEC system works. The dual lobe system works as the low lobes deliver low-end efficiency and torque for drivability while the high lobes supply power for higher rpm. The VVL system is a more effective setup than the variable cam timing (VTC) found on the DE/DET cylinder heads.
Another big advantage the VE cylinder head has over its DE/DET counterparts is valve rocker assembly design. The VE valve rocker assembly pivots off a dowel and never dislodges unlike the DE/DET, which uses a floating rocker assembly. This dowel design offers improved reliability and efficiency when looking to increase horsepower levels. Due to the fact that it is shaft mounted, the fork will not rock sideways from valve to valve like the DE/DET. This sideways motion can lead to spitting out rocker arms and damaging the engine, which has been a common occurrence with many non-VE cylinder heads. And lastly, the VE heads are designed with larger sized ports in comparison to both the DE/DET heads to deliver more airflow and pave the path for increased power potential.
Cylinder Head Massaging
Just like the block, the factory head design has its positives and negatives. The intake ports are proportionately sized and known to outflow the SR20 DE/DET cylinder heads but with a bit of massaging, there’s also room for further improvements. Shingo Yugami—Bluemoon Performance’s engine specialist with 25 years of automotive repair and tuning experience—suggested we simply clean up the cylinder ports without altering the shape of the bowl. Too often enthusiasts become overzealous with the “bigger is better” mentality, and begin grinding away at the ports, only to realize that their car performs with little to no throttle response. Since our Datsun 510 project was slated for street driving, we weren’t shooting for a monster cylinder head port that would ultimately kill our low-midrange horsepower and response.
The real focus points of the porting are the merge, throat, and valve pocket. When closely examining the stock SR20VE head, it is apparent that there is quite a bit of material that can be eliminated at the port divider towards the intake and exhaust sides. Cutting away at this material will open up the passage, increasing the capacity of air that can be inhaled and exhaled out the engine. The second image above details the passage after Bluemoon Performance made the modifications.
We chose to increase the size of the stock valve to Supertech 35.15mm nitride stainless intake valves and 31.5mm 751 Inconel exhaust valves. The 1mm increase on the intake valve and a 2mm increase on the exhaust valve allows a gain in midrange torque and a slight bump in horsepower when accompanied by bigger camshafts, headwork, and a good intake, header, exhaust combo. However increasing the valve sizing too much can affect overall engine performance, and can actually reduce flow at low lift.
The valve throat opening also has to be substantially expanded to accommodate the larger diameter. Without opening up the throat there will be a flared ramp at the valve opening, in effect not fully taking advantage of the larger diameter valve. The intake valve is coated with a black nitride, characteristically smoother than a chrome finish. This lowers the friction coefficient between the valve and the guide. For its ability to withstand extreme temperatures, Inconel is used for the exhaust valves.
With all our parts in hand, we paid a visit to cylinder head specialist Tom Fujita at Port Flow Design located in Harbor City, CA—one of the leading authorities in cylinder head performance. Tom’s expertise was derived from working as an engineer in Nissan Motorsports’ IMSA program. His clientele is extensive and consists of current and former SCCA, NASCAR, and NHRA competitors who rely on his quality machines and workmanship.
Fujita installed our valvetrain components including the Supertech titanium retainers, double valve springs and valve guides, and resurfaced the cylinder head. The Supertech exhaust valve was cut back from +2mm to +1mm to minimize the exhaust escape velocity, which is critical to the process of scavenging and creating power for our street driven car. Each valve was then clearanced to the guide, around each valve was de-shrouded, and the seats received a radius valve job.
A radius valve job consists of cutting the seats with a special carbide cutter. The Newen CNC machine used by Port Flow Design is specially made with the best angles already shaped into the cutter to ensure you get the perfect seats. This is a substantial improvement over 3 and 5 angle valve jobs, which are known to leave ridges at the transition. The radius seat eliminates the ridges and leaves a very smooth surface.
With our cylinder head refreshed and back in our hands, we began the arduous task of re-shimming for the new camshafts. Anytime cylinder headwork such as installing or replacing camshafts and valves is performed, you must shim the valves to allow proper clearance for the cam lobes. If this is not done, the cam will not contact the rocker squarely, leading to loss in power or even worse, excessive valvetrain wear. Installing the new camshafts in our VVL cylinder head proved to be a lengthy process, since the VVL cylinder head uses these shims.
Using Harley-Davidson parts for our engine build might sound crazy, but using motorcycle shims became a reality of our build. The Hot Cams valve shim kit was originally designed for a Harley-Davidson V-Rod, but we found it to be an affordable alternative to purchasing OEM Nissan shims, which would cost $14 each multiplied by the 16 shims needed equals a total of $224. While the kit provides a large number of shims ranging in thickness, we found that the .050mm increments might not offer enough variation for proper adjustment in all cases, like a .025mm increment would.
Due to this minor setback, a few of the shims required sanding and grinding down, in order to optimize valve clearance for the new Kelford Camshafts. Using an emery cloth while wetting it with WD-40, I proceeded to slowly remove material. The important thing to remember is to remove material off the shims while keeping it flat as possible and taking measurements along the way for exact tolerances. The process took a long time—about 2-3 minutes of sanding to get 0.0005″ of material removed. Each shim was carefully measured using a micrometer to achieve proper thickness. This procedure is often a costly, time-consuming process when asking a professional mechanic, but is an important procedure that should not be ignored.
Kelford 184-C Racing Camshafts
There are a lot of variables to consider when upgrading your factory camshafts including duration (how long the valve stays open), lift (how far the valve opens), and overlap (how long the intake and exhaust valves are open at the same time). Early intake valve opening is beneficial to both good and poor flowing intake ports. It allows the intake valve during high acceleration to deliver as much mixture to the cylinder in the shortest time possible. The exhaust port flow and exhaust-closing event will determine how early you can open the intake valve. An earlier intake valve opening will increase the overlap period where both the intake and exhaust valves are open. With a poor flowing exhaust port, an earlier intake valve opening can cause the exhaust charge to pollute the intake charge.
In selecting a camshaft that would work well with our current setup, we contacted Kelford Cams, located in Christchurch, New Zealand. Kelford specializes in custom camshaft design and manufacturing for all types of engines. Their 184-C racing camshafts were designed specifically for the SR16/20VE, and offers lobe profiles which are easy on valvetrain components, yet recommended to be used in conjunction with performance valve springs and retainers on high-revving engines.
Data gathered from various tuners on the SR20VE P11 factory camshafts revealed that at 6,000 rpm and higher, the stock cams showed severe intake air restrictions and showed a dramatic drop in power. The Kelford 184-C racing camshafts are designed and tested to be a good street/strip grind camshaft with 314/312-intake/exhaust duration and 12.50/11.80mm lifts on the high lobes while the low lobes come in at 252/248 duration-intake/exhaust duration and 10.2/8.3mm lifts. The company claims their 184-C camshafts are good for mid and top end performance, suited for modified and high-compression motors. We plan on putting these cams to the test to prove it delivers the power they claim.
Aftermarket camshafts sporting aggressive durations are really made for use in the range above 5,500 rpm. This is not typically the drivability you would want from a street car, but we plan to test this setup to determine what works and what doesn’t. In the past, the 184-C camshafts have been proven to deliver amazing power among high-compression front-wheel-drive SR20VE owners.
Taarks VVL Solenoid Relocation Block
There are two options for VVL solenoids, the P11 dual solenoid block, or the P12 Single solenoid block. Since the VVL head requires oil pressure to activate the solenoids, we modified the P11 dual solenoid block system in order to allow it to fit in our cramped engine bay. There’s simply no room for the VVL solenoid when the engine is mounted in a RWD configuration between the head and firewall.
To remedy the issue, we purchased a set of VVL solenoid relocation blocks from Taarks, located in Queensland, Australia. The solenoid relocation blocks are CNC-machined from T-6061 billet aluminum and designed with a super low profile to allow maximum clearance to the firewall. Both the Taarks relocation block and oil block—containing a VVL feed hole on it—work in conjunction to make the RWD conversion an easier process.
Using the solenoid relocation kit requires modifying the OEM solenoid brackets. We cut the OEM bracket and fabricated some mounts to secure the unit onto the center of the block. The relocation kit comes with Viton O-Rings that eliminate the need for a gasket. ORB fittings are also included in the kit, which allow the installer to use larger sized oil lines matched to the head—the way Nissan intended.
Taarks Crank Angle Sensor
Running a VVL head on a RWD block requires removal of our OEM distributor due to firewall clearance issues. One option is to keep the distributor and cut an unsightly hole into the firewall, the other is to bypass the distributor by using a Taarks crank angle sensor (CAS). In this case, we chose the latter of the two. This cam trigger wheel uses a magnetic Hall pickup to provide the ECU with a trigger and home signal to any aftermarket ECU, which is less prone to fluctuations/dirty signals.
Installation of the unit is straightforward, as it is a bolt-on piece that requires no machining of the cylinder head unlike their competitors CAS design. The kit can be installed with the cylinder head already bolted onto the block. It mounts by using the 24mm OEM camshaft bolt to attach to the exhaust camshaft sprocket. However, it requires replacing the OEM dowel locator pin with a supplied longer sized pin, and removing the front freeze plug where the hall sensor will be fitted into place.
Taarks also offers a CAS block-off bracket to plug the factory distributor location. Some final steps include edging the valve cover with a grinder to clear the hall wheel from rubbing.
Taarks SR20VE RWD Water Neck
When converting the SR20VE to a RWD setup, a custom water neck becomes a necessity. This aluminum water neck allows the factory coolant hoses to properly align with the cylinder head. We welded on a -10AN bung fitting to accept the braided lines connected from the water heater to the cylinder head.
Mating the SR20DET S15 6-speed transmission to the R200 rear differential required us to Frankenstein a driveshaft using a number of different parts. The SR20DET S13/S14 driveshafts come from the factory as a two-piece design. Our one-piece setup was purchased used but was originally sourced from The Driveshaft Shop and consisted of an S15 front yolk with larger Spicer 1310 axle joints.
It was measured and sent to Driveshaft Pro located in Westminster, CA, to be shortened, re-welded and balanced.
The differential axle flange on our R200 was originally provisioned for the S30 280ZX driveshaft and didn’t align with our new custom piece. Rather than search for a new flange, we replaced the differential flange with an earlier model 1989 S13 240SX to produce the perfect fit.
AEM Electronics CDI Pencil Ignition Coils
AEM’s Electronics CDI Coils were designed to convert distributed ignition systems over to a more modern coil-on-plug setup, eliminating the need to replace your aging cap, rotor, and wire assembly. The kit not only helps to clean up the engine bay but also increases spark output over standard coils and is ideal for use in high-boost, high-rpm, or high-compression engines.
CDI systems are ideal for use with standalone programmable engine management systems, which allow for individual ignition trim tuning.
Koyo’s release of their new Datsun 510 radiator couldn’t have come at a better time. The performance radiator is manufactured with a 48mm crossflow core design, Noclok R-brazed for strength and reliability, and bolts to the factory mounting points.
In order to keep our high compression motor’s temperature in check, we fabricated some brackets to attach a Derale single speed electric fan with a molded shroud—originally designed to fit classic Ford Mustangs. Delivering 2150 CFMs, this electric fan should have no problem keeping the notoriously temperamental SR20 engine in check.
Because this radiator was designed for the factory L-series engine, we removed the original water ports and welded on a -16AN bung provided by Taarks Performance. Taarks also supplied us with billet water neck adapters for the block. We finished off the cooling system with some custom crimped Brown & Miller Racing Solutions PTFE hoses.
Stay tuned, we’re finally rounding third base and sprinting our way to home plate to complete our engine build. With plenty more custom fabrication and trick components to add to our SR20VE hybrid build, the fourth and final segment will be definitely worth the wait!