KILLER K20
HONDA K-SERIES FRANKENSTEIN BUILD PART ONE
Arguably the most popular and sought-after four-cylinder engine of our era, the Honda K20A2 has become the LS of the four-cylinder import world; you can find these engines in almost anything these days, half the time in all their scrapyard unopened glory. While the blocks are square in architecture, with an 86x86mm bore/ stroke, and come with tough components such as a one-piece main cap girdle and forged crank, it’s the performance of the Type R’s head that is the main reason why these engines are so popular. They flow some impressive figures in factory form and outperform many modified heads. This is also why you see so many of these heads ripped from the comfort of the two-litre and slapped onto the bigger capacity K24 bottom end, as seen on page 28 of this issue.
None of that matters here, though. What we are going to build is a junkyard dog, but the end result will be anything but. Forget spending more than $2K for a used K20A2 long block; we’ve raided the wreckers and will be piecing together our Frankenstein engine using minimal Type R components.
The reason is that this K20 is to be built to run quarter-miles on dirt and in an oval, so the requirements for the engine are different from those for an all-out drag engine or a circuit-based race motor. We are looking for a big power band here, as fat as we can get. However, the rules for the motor’s destined class of F2 midgets throw a spanner in the works, as they require a 32mm restrictor in each intake runner. The rules for the engine internals are loose as long as no titanium is used, capacity doesn’t exceed 2050cc, and variable valve control such as VTEC is deleted.
The Plan
The basis for the engine is a K20A (Eco block) that we picked up from the wreckers with only 68,000 clicks on the clock. Unlike the Type R (K20A2) variant, it’s a much lower compression engine (9.0:1 versus 11.0:1) with no forged crank, and only intake-side VTEC and 1mm smaller intake and exhaust valves. The only thing we will be keeping from the head is the exhaust-side roller rockers; the rest will go into the bin. We will be back at the scrapyard shopping for a second set of roller rockers to use on the intake side in the new head. While you can buy fancy kits, this is a budget option to keep costs down, but it will cost you rpm due to its weight in comparison with the aftermarket options. With our desired rpm range, we will be using stock Type R cams on both the intake and exhaust, coupled with Drag Cartel adjustable cam gears.
The head we’re using is a K24 RBB casting. While these are not hugely popular in engine swaps, for our application, the smaller ports are what our cylinder-head specialist believes will be perfect to work alongside the 32mm restrictors. The head will spend time on the Horsepower Heads CNC machine to be reshaped in a few areas, but will not be overly ported, and will have 1mm oversized intake valves. The valves are 5000-series Ferrea stainless items, and we’ll use Kelford springs, plus manganese bronze guides and special valve seat inserts to suit the fuel of choice: methanol — in an engine that’s using pump gas or such, these would not be needed, but methanol is very corrosive.
Our 68,000km block was found to be in great condition, but will still be getting oversized by 1mm to sneak in as much capacity as we can. The crank is a second-hand Type R and will hold a set of I-beam Pro-A rods from Carrillo. These are Carrillo’s economical I-beam, but, as we’re not boosting the engine or revving it too the moon, they are the perfect lightweight choice for us.
Our pistons are from Wiseco, its high-compression offering in K20 of 12.4:1 and 1mm oversized at 87mm to make the most of the class maximum cubic centimetres of 2050. We will be using ACL race bearings throughout. The block itself is off being machined to suit, and we will cover that in the next issue, when we dig into assembly and prep.
Like all K-series blocks, the block is ‘open deck’, meaning that the steel cylinder bores are unsupported in the top. In racing application, where high rpm is often the norm, the bores are known to oval, especially when oversized. While a full sleeve job is often considered the best option in this case, block guards, like the billet one from ASP that we’re using, are a cheap alternative and stiffen and support cylinders.
By next issue, we should have everything back from the machine shops and ready to assemble, so check back if you’ve ever wanted to piece together your own race engine.
1. FIVE-STROKE
We’ll kick things off with something you will probably see in production in the very near future. It’s a take on the conventional four-valve engine, except that it allows an additional combustion cycle. So, instead of the spent exhaust gases exiting post-combustion, they are sent into another combustion chamber and compressed for a second time before being exhausted. This second combustion chamber is twice the bore of the first and is common between two fired highcompression cylinders. This effectively increases the expansion ratio of the engine without the side effects that you’d get with an impossibly long stroke.
2. DUKE AXIAL ENGINE
Developed right here in New Zealand, the Duke axial engine looks like something that belongs in the front of a World War II fighter. Ditching the traditional crankshaft, the cylinders are parallel to the main shaft, with the combustion forces acting on a reciprocator that oscillates around the main shaft in a wavelike motion. Similar to the rotary design, the cylinders slide past both an intake and an exhaust port. A spark plug deletes the need for a valvetrain. Each cylinder completes three power strokes per revolution! All this adds up to one very lightweight, compact, and powerful engine.
3. VC TURBO
Just released by Infinity, ‘VC’ stands for ‘variable compression’ ratio — yes, you read that right. Essentially, the stroke of the piston is adjusted to affect compression from 8.5:1, when you’re hard up it, to 14.1:1 during idle and high cruising. How? Instead of the rod connecting directly to the crank, it connects via a bell crank, which centres on the crank. The other end is connected to another cam-like shaft, which is elliptical and controlled by an actuator. The engine also uses a mix of both conventional and direct injection.
4. GASOLINE COMPRESSION ENGINE
Getting diesel-like mileage from a petrol engine is the dream of many manufacturers, but who knew achieving it would be so damn simple? Using compression ignition like a diesel, this 2.7-litre three-cylinder engine uses opposing pistons in each cylinder to compress the air– fuel mix until it ignites, driving two crankshafts joined by one larger gear drive. The first production version is set to hit the market in the US, powering the F-series Ford trucks and offering 201kW and 650Nm.
5. LIQUID PISTON ENGINE
Here’s one for the rotor-heads out there. It takes the traditional Wankel rotary engine to the next level. An eccentric shaft is driven by an ovalshaped rotor that spins inside a housing. The rotor actually carries the air–fuel mix through the combustion cycle, allowing the engine to have a constant volume — unlike a conventional engine, which has constant pressure. Maintaining constant volume in the combustion allows for a higher compression temperature and better atomization of the mix. In short, it’s a far more efficient combustion.