OK, you looked at the title and thought to yourself what!? We don't blame you. But engine build stories have been done over and over again. When you've been doing stories on engines for this long, it's hard to think of new ones to do. But what better to work with than the bastard child of Nissan motors. The KA24DE has been long neglected for the SR20DET and, more recently, the VQ35DE as an alternative powerplant for the S-chassis car. But there has always been a group of true believers in the KA. So in deciding on a new engine build series, we landed on using the KA24DE and sought out Naoto Negishi of NPD to aid with the build. Owning a 240SX for his first car (in 1994), he has been a longtime fan of the KA. He has always preached to us the power of the KA as we sat quietly chiding him along and comparing the "truck motor" to the more performance-orientated SR20DET. Naoto and his passion for all things KA24DE has been recently developing parts for the KA under his company NPD with some amazing results. Follow along as we begin our quest to eclipse the 700hp marker and take you through the build-up process and discuss how this project can be applied to your own motor build in the near future.
Our build will go into every aspect of the KA24DE engine-from the parts being used to addressing weaknesses in the motor. First, we will give an overview of the KA24DE, the bottom end parts we are going to be using and how to properly prep the stock bottom as it leaves for the machine shop. The overall target is 750 bhp at 8,000 rpm on the engine dyno. Yes, we know this sounds too good to be true but never say it can't be done in the world of high performance.
In its stock form, this truck...
In its stock form, this truck motor will be transformed into a 750bhp powerplant.
So, why a KA24DE? For starters, the155hp 2.4L engine comes in the USDM S13 and S14. The large number of Nissans running this engine plus the popularity of swaps (dumping in favor of a SR20DET), makes the engine readily available and cheap. You might say, "Honda SOHC D15B motors are plentiful too," but that doesn't make them good. While the single-cam Hondas are popular among diehard H-badge fanatics, they lack the 89mm stock bore like the KA24DE and cast-iron block and main caps that utilize a girdle design. So, out of the box, the KA24DE it is built to withstand some punishment. Before you jump to conclusions and ask yourself: "Besides a big engine what else is it good for?" The intake ports on the cylinder head are large from the factory and utilize a high-degree port angle. The valvetrain also utilizes a direct-bucket design. This means you don't have the problems of rockers popping out or failing like the SR20DET.
While we briefly covered the basics on why the KA24DE is an ideal candidate, we should also include the numerous issues associated with the motor. All in truth, if this was such a perfect motor everyone would be using it right? These sure are, but before we crank up the boost and try to peg the 750 marker we took the time to carefully analyze the engine and its downfalls starting with the bottom end. The cast pistons and weak rods were designed with no intention of taking any abuse. The media-type headgasket would definitely fall apart under any serious boost. The crankshaft is only half-counter balanced. The head bolts are a measly M10 (SR20DET is M12 and RB26DET is a M14).
The stock valvetrain utilizes...
The stock valvetrain utilizes a direct-bucket design, eliminating the rocker arm problems associated with SR20DET motors.
Although the intake ports are decent in terms of flow, the exhaust ports are the direct opposite. They're flow restrictive and don't have a very good port angle. The cam gears are so small that you cannot utilize a veneer-type adjustable cam gear (slides for adjustment); you can only use a knock-pin type (moves to lock in a permanent position).
Although the SR and RB engines all use a direct-ignition-type system, the KA still uses a distributor type. It's obvious that the motor was not designed with high performance in mind. So what can be done to transform this block of stone into David? Well to begin with we decided that it has to get turbocharged. To do this, however, we would have to make sure the block could withstand the type of power we would want to see.
 The factory headgasket is...  The factory headgasket is a puny media gasket type. We will be replacing it with a metal-type setup from Cometic. |  The exhaust ports on the head...  The exhaust ports on the head are much smaller compared to the intake side. Much of it will need to be ported to reach proper flow for high-power output. |  On the SR20DET and RB26DETT...  On the SR20DET and RB26DETT the ignition is a coil pack-based system. The KA still utilizes a distributor system. |