Building A Nissan KA24DE Motor - Tech Knowledge

Over the course of the past year, our sister publication, Turbo Magazine (bless her soul), has been following along on a unique buildup of a KA24DE engine--the ubiquitous 2.4L engine produced from July 1988 through January 1996, powering numerous Nissan vehicles ranging from the sporty 240SX to the sport-ute Pathfinder. Now, you might be asking why anyone would want to build the KA24DE; it's a 65hp/L truck motor that everyone junks for the SR20DET. There's no denying that, pound for pound, the SR20 has its advantages over the KA24 in stock trim. We skeptically took a look at the initial build of the KA24DE and did a double take when we found out that the motor is slated to make 750 bhp! This isn't your run-of-the-mill build, and with Naoto Negishi of NPD as the mastermind behind the project, nothing is impossible. Naoto is more than familiar with extracting big power from import cars. His past builds include a list of GT-Rs, including a 1,100whp beast now roaming the streets of the Midwest. With the demise of Turbo and the cult following that ensued during this KA24DE buildup, we decided to pick up where they left off--but not before we updated our readers with a recap, including some significant transformations. Stay tuned, as we continue the build in our upcoming issues wherein NPD attempts to break 750 bhp!

The starting point of the...        read full caption The starting point of the build was identifying the flaws and weaknesses of the KA24 and reinforcing it to withstand the harsh pressures of 750 bhp. We knew that the crank, rods and pistons all had to be replaced. Since the stock crank is only half counter weighted, NPD developed a fully-countered crank in conjunction with BC (Brian Crower).	We're using BC connecting...        read full caption We're using BC connecting rods, and NPD-spec Supertech 9.5:1 pistons, featuring a box skirt design with less weight at the end of the reciprocating mass. Each piece was blueprinted and balanced to NPD specifications. Our block was sent over to Ultra Performance Machine to be bored, honed and decked. All friction surfaces were also prepped by WPC treatments. This includes the bearings, pistons, pins, oil pump gear, housing, block, and crank. AMS provided both the upgraded main and head studs.	We ran into a slight problem...        read full caption We ran into a slight problem with the new crank. Since the factory crank is only half counterweighted, the factory block is cast with this in mind. Unfortunately for us, our new, fully-countered crank hit against small sections of the block and girdle. The block had to be modified, and we also deburred any casting flash to promote oil flow, while ensuring no debris would enter the lubrication system. The girdle was also clearanced for the now fully-countered crankshaft. The bright side to modifying the block is that the area interfering with the crank has no real critical usage and can easily be grinded. Since we were already grinding away at the bottom, we decided to clean up any left-over casting imperfections.
Mike McDaniel, of Engine Supply...        read full caption Mike McDaniel, of Engine Supply in Santa Ana, CA, made a couple of passes with the bore machine to determine how much material had to be taken out. Remember, it's easy to enlarge the bore, but impossible to make it smaller. We went from the stock 89mm to a 90mm bore. Having a general reference of how much material each pass removed gave them a general idea of how much they needed to bore the block to get to the general area in which they needed to be. Once the machining was done, we measured the block again. We were within our 0.01 mm out-of-round tolerance and the final hone was within our piston-to-wall clearance. Our block was now ready to be taken back to the shop to be assembled.	Utilizing a billet fully-countered...        read full caption Utilizing a billet fully-countered crank will add the extra insurance under boost and allow us to run the engine at higher RPM with less vibration.	With so much lift from the...        read full caption With so much lift from the new camshaft, the BC cams need to be clearanced with the head. NPD stresses the importance of first test fitting before final installation.
The real focus of the porting...        read full caption The real focus of the porting is at the merge, throat, and valve pocket. If you closely examine the stock KA24 head, you'll see that there's quite a bit of material that can be cut out at the merge between the two exhaust passages. To a lesser degree, the merge on the intake side is narrowed. Cutting away at this material will open up the passage, increasing the capacity of air that can be exhaled out of the engine. The valve pocket was raised on both sides to increase the capacity of the port. The ramp was left relatively unchanged on either side. Special attention was given to the tiny exhaust ports--a handicap for the KA24DE engine.	WPC treated the metal with...        read full caption WPC treated the metal with their propriety technique, hardening the surface and creating a dimple effect. This promotes oil accumulation, increasing the effectiveness of protection between friction surfaces. The camshafts were swapped for a 272-degree BC Stage 3 with 10.19 mm of lift. This is a huge difference compared to the stock bump sticks, which have 256 degrees and 8.73 mm of lift. To ensure proper cam timing, Jim Wolf Technology cam sprockets were dialed via a timing wheel and dial gauge.	Supplying the boost behind...        read full caption Supplying the boost behind this beast is an HKS T51R SPL turbo. Yes, the same one reserved for Supras and GT-Rs is force-feeding this KA24DE. When questioning Naoto about his choice, it became apparent that it would take a large-frame turbo to handle the task of making 750 bhp. Keeping boost pressure in check is a Turbosmart PowerGate 60mm wastegate. On the intake side, an original NPD surge tank replaced the stock intake manifold. To keep the intake charge from bottlenecking, an 83mm Q45 throttle body was chosen over the stock 60mm unit. To increase the availability of injector choices, a GReddy top-feed injector rail was installed.
Another major weak point for...        read full caption Another major weak point for the KA24DE is the head. Its ports are tiny when compared to the SR20DET. We had Tom over at Portflow rework our head to increase air flow and install a set of Supertech 37.1mm nitride intake valves and 32mm Inconel exhaust valves and guides. To ensure consistency throughout the valve train, Naoto tested each valve spring individually. Supertech also provided us with their inside shim kit, reducing the overall weight of the buckets.	NPD's plenum is made from...        read full caption NPD's plenum is made from TIG-welded, die-pressed sheets of aluminum, and are designed for high boost applications. The GReddy top-feed rail feeds a set of 1,600cc injectors.	Since adding on a turbo and...        read full caption Since adding on a turbo and an oil cooler to an engine not originally designed for them, NPD wanted to increase the oil capacity of the engine. Opting for Xcessive Manufacturing's oil pan extension, a GReddy SR20DET oil sump could then be incorporated. This increased overall oil capacity by 1,000 cc. The distributor was ditched, since Naoto decided to use coil packs from Okada Projects instead. A custom machined adaptor plate was welded to the valve cover to receive the coil packs, originally meant for a Honda S2000.
A common misconception is...        read full caption A common misconception is that 0 degrees on a cam sprocket is where timing should be set. The truth is, 0 degrees is irrelevant when using aftermarket cams. It is used only as a starting point, and should never be set without properly degreeing the cam. After determining the centerline of the cam, Naoto made the proper adjustments and set the cam timing at 116 degrees intake, and 116 degrees exhaust. Naoto's experience with other fixed-valve-timing turbo engines has shown aggressive (top-end power biased) cam timing in the area of 108- to 112 degrees and milder (lower- to mid-range) settings at 118- to 122 degrees. Since 116 degrees is stock for the S14 KA24DE, and close to the middle, he decided leave it there and perform final cam timing on the dyno.