In the last installment of the Si sedan project, I mentioned that eventually the K20 bottom end would make way for a K24 block, and finally, that time has come. Having driven the ninth-generation Si for a few weeks and getting a taste of the 2.4L torque, I was obsessed with doing this conversion before years end. The K24/K20 combo is really nothing new, and over the past few years, the eighth-generation Si crowd has really taken a liking to the swap, and why not? The two engines share so many similarities and work so well with another that it's almost a shame not to.
The foundation - KMOD Performance
Finding a K24 block isn't impossible, especially since they were standard in vehicles like the Element, Accord, TSX, etc. After searching for a block online, I came across KMOD Performance in Asheboro, NC. I'd heard the name previously, as their All Motor RSX Street build had nailed a 12.1 and their turbo RSX street competitor held a 10.20 under its belt. Impressive numbers, and I found that not only do they stock and sell built K24 blocks; they have a number of years of experience behind them. KMOD offers just about every possible K-series configuration you can imagine, from mild to wild, including custom-built K-series turbo kits, K24/K20 combos, even complete crate engine packages that don't require a core exchange. Though you can find B-series build options on their website, their specialty is undoubtedly the K-series family along with high performance transmission builds. With roots planted way back in 1996, KMOD, now a three person crew consisting of owner Marquis, his wife Linda, and employee Octavio, they've been building N/A, nitrous-fed, and turbo Honda engines of various generations for years. Currently based out of an 8,000-sq-ft facility, KMOD builds and ships engines worldwide at rate of approximately 40-60 per year!
You can no doubt build an entire crate engine through KMOD's website and choose your compression, bore size, add a header, cams, oil pump conversion and so many other options that you'll be in awe at all of the choices. For myself, only a block was needed since I'd be reusing my K20Z3 head. I contacted KMOD and explained what mods I was thinking about and what my intentions with the car were. I was presented with a number of options, and ultimately I went with an 87.5 bore and 12.5:1 compression block. I'd be supplying my own rods and pistons, but again, all of that is available directly through KMOD so you can build exactly what you want as these guys offer everything from 220hp street engines, to 300+hp, naturally aspirated monsters, even 750+hp turbo engines.
The KMOD Performance-built K24 block, which originated from a Honda CR-V, features K1 Engineering rods and 12.5:1 JE Pistons. Truly a one-stop engine building shop, KMOD can custom build just about any K series configuration you can come up with, whether it be NA or turbo.
The hard parts - JE Piston, K1 Technologies and Golden Eagle mfg.
You can't really conjure up a piston size or compression ratio that JE Pistons can't tackle. Over six decades of standing proudly at the forefront of the performance industry will do that to a company. While this is only a daily driven streetcar, if you're anything like me, you want the best when it's within reach. The fact that JE Pistons supplies slugs for everything from NASCAR, to NHRA, to ALMS, and have helped to power some of the fastest drag and road race cars in the world, you know that you're in good company. Holding tolerances to a millionth of an inch, JE's advanced processes are essentially unrivaled. I contacted JE Pistons to request a set of 87.5mm pistons at 12.5:1 compression for the K24 block. Along with my order, the JE tech requested the camshaft specs that I'd be using for the build to verify clearance and just a few weeks later, the pistons were on my desk awaiting duty.
To match performance with the aftermarket pistons, a set of I-beam, forged 4340 steel connecting rods were ordered from K1 Technologies. Shot peened for improved fatigue life, utilizing bronze wrist pins and ARP 2000 hardware, each set of rods is weight matched to within 1 gram on each end. With both the rods and the pistons on hand, I shipped them off to KMOD for balance and assembly. Not long after, I had a 160lb package delivered to the office. Speaking of that package, an important factor when having something like a block shipped is how it's packaged. KMOD prepped the block, then wrapped it in a protective seal, and strapped the block to a solid wood foundation. They then surrounded it with plenty of cushioning in case of the unthinkable, boxed that up, and finally, they sealed everything and strapped it to a large pallet. Unless someone removed the heavy-duty straps and literally pushed the block over, it wasn't budging at all-KMOD did it right.
To mate the old head and new block together, Golden Eagle supplied their K20/K24 headstud kit. Produced in high quality 8740 material and heat treated way beyond anything your engine will ever see, the headstuds provide some added security as they were designed to withstand turbo, nitrous, and full race engines, far more abuse than a streetcar will ever see. Fitment is factory fresh and it comes with all of the hardware you'll need to marry the two halves properly.
The ancillary parts - AutoFair Honda (AFH)
When I first began researching what would be needed for the K24 block swap, I quickly realized that it wasn't quite as simple as just tossing in a block and a K24 timing chain. There are a number of OEM parts needed to do the conversion properly. I contacted AutoFair Honda of Manchester, NH for two major reasons. The first being they offer multiple K-series parts and packages on some of the popular Honda forums like Honda-Tech and 8thcivic. Their pricing is brutally competitive and they even help take care of the guesswork by eliminating what you don't need, and including exactly what you will need. The second reason had more to do with their growing reputation for excellent customer service and a vast knowledge of all things K-related. So how did a team of three that spent time mingling on k20a.org become an online OEM parts supplying juggernaut? Well, it began with Parts Manager Rich St. Jean, who started off by offering RRC intake manifolds online. Brand new at the time, it brought about incredible interest from enthusiasts; so much so, that Rich hired Ryan Doolin to help meet the demand in hopes of continuing to grow the business. With Ryan taking the reigns online and business picking up rapidly, Colin McKeever was also brought on board and these two have pushed online sales and service to a whole new level. The difference between most of the online dealer sites and AFH, is that these guys are just like you and me. That is, they live and breathe Honda parts, builds, and go-fast options. As Colin puts it, "each of us has their own builds and just wants to go faster. In turn, we want to help the enthusiasts reach their goals because we're just like them ... we ARE them."
With a consistent inventory of OEM goods from the D-, B-, H-, K-, and F-series families, the duo has recently branched into Facebook and Instagram territory to open even more lines of communication with enthusiasts. Additionally, they've created two spin-off sites, afhkparts.com and afhparts.com, both of which stock countless OEM parts and packages, as well as a hand-picked line of aftermarket products well known to be beneficial to K-swaps and K24/K20 conversions.
When I approached the AFH crew about the project, it took only minutes to get a breakdown of exactly what I'd need to do the conversion properly. Ryan compiled a list of parts including a K20A2 oil pump conversion, something they package with all necessary supporting parts so that you're not hunting for that extra bolt or wondering what you might have forgotten when you ordered. Here is Ryan's list of necessities (all of which AFH keeps in stock, ready to ship):
- K24 timing chain cover
- K24 timing chain
- K24 timing guide
- TSX head gasket
- CRV passenger side mount bracket
- PRB oil pump conversion kit:
- K20A2 oil pump
- K20A2 baffle plate
- K20A2 oil pump chain
- K20A2 oil pump chain guide
- Bolts for the oil pump and baffle plate
- Bolt and washer to plug oil jet on the block
Air and bumpsticks - Kelford, Skunk2, Hybrid Racing, P2R
In the camshaft department, Kelford 179-Bs were enlisted, and feature a 306/298 duration and best suited for high compression aftermarket pistons with deep pockets for clearance. Kelford states that the 179-B is much more aggressive than their 179-A series drop-in cams, but like the As, they're easy on the valvetrain and timing chain making them perfect for long term use-whether that's endurance racing, street duty, or both. Backed by the Supertech valvesprings and retainers that we added in a previous installment, the Kelfords looked to be ideal for this combination of parts, and the dyno sheet at the end of this article will attest to that.
To help bring more air into the 2.4L mill, Hybrid Racing provided their 3.5in cold air intake intended specifically for the eighth-gen. Using a 1/4-inch thick fiberglass-reinforced silicone construction, the intake charge is kept cooler than traditional aluminum intake piping. A 6-inch velocity stack and accompanying air filter are positioned just outside of the engine bay, behind and below the driver side headlight. Though we don't get much rain in SoCal these days, if the filter were to be submerged in a puddle, Hybrid's injection molded bypass manifold, which also houses the factory MAF sensor and hose ports, contains an air bypass feature that offers some additional insurance in case of the unthinkable. The silicone intake is attached to a Honda factory J35 throttle body, which is larger than the factory unit and is drive-by-wire.
The factory RBC intake manifold is a solid performer. In fact, many with K-swaps reach for the RBC unit because of its effectiveness and affordability. There are options for improvement, and Skunk2's Pro Series intake manifold is one of them. While I wouldn't have seen much of a difference at all in using this manifold with the mild bolt-ons I had on the 2.0L, the new set up would certainly benefit from the larger plenum and short, slightly larger runners. The cast aluminum manifold also comes with an insulated gasket and is a direct bolt-on.
In order to bolt the J35 throttle body to the Skunk2 intake manifold, an adapter was needed since the bolt pattern on the J series throttle body isn't the same as the Si. Power Rev Racing (P2R) has really filled a niche with a throttle body spacer and adapter plate line up. Featuring a dual bolt pattern, one drilled for the throttle body, the other for the manifold, it makes quick work of joining the two pieces. Produced in billet aluminum and precision cut, these adapters feature an OEM fit and for some applications, are available in different colors.
There aren't many headers that will clear K24/K20 eighth-gen sub-frame properly, especially with aftermarket mounts. I had to search online to find a used Skunk2 Megapower which does in fact clear and is well known to make great power with the K series engine in both original and 2.4L conversions, but isn't being produced any longer. A custom-built header would be ideal, but time constraints didn't allow for it.
Fuel and grab - Deatschwerks and Spec Clutch
Deatschwerks offers a full line of injectors and fuel pumps and they've really hit their stride in the import performance realm as of late. After explaining the engine set up, Deatschwerks recommended their DW65C fuel pump to get things started. They've managed to pack a 265lph, E85 compatible pump into an ultra quiet package. With modern day management systems, you really can't go "too big" with injectors (within reason of course) so I chose a set of Deatschwerks 600s. I won't need that much for this particular configuration, but proper tuning will trim the fat so to speak, and I have plenty of room for growth if I decide to go a different route. As with all of Deatschwerks injectors, flow rates and set balancing is done in house and balanced within 1-2 percent. A flow report comes standard with all of DW's injector sets and like their fuel pumps, they're E85 compatible.
Spec Clutch offers a number of different stages for the eighth-gen Civic, each carrying it's own torque capacity rating. I chose the Stage 2+ and aluminum flywheel and after driving the car for the last few weeks, I'm 110 percent sure I made the right choice. Everyone wants a clutch that will grab aggressively, but those that daily drive their cars don't want a sore left leg after crawling through unavoidable traffic-something you won't get with Spec Clutch's Stage 2 and 2+. The 2+ has a torque rating of 300 and though I had no plans to make that kind of power, its pedal feel is the same as the Stage 2 (torque rating 260) which, by the way, is incredibly light and almost factory-like. The drive to the dyno and back was filled with stop and go traffic so I got the chance to work the clutch pretty much non-stop. The engagement was crisp and once again, very light, but there isn't even a hint of slipping under "abusive" driving. Rock solid with an OEM feel? I'm in. Just a warning, if you talk to me in person and ask about the car, there's a pretty good chance I'm going to blab on and on about the clutch.
K-Series gurus - Sportcar Motion
With the KMOD block and all of the parts on hand, I turned to Loi Song and his crew at Sportcar Motion. Over the past few years, SCM has become the go-to destination for all things K-related. Straight swaps, fully built race engines, or the increasingly popular K24/K20 8th gen conversions, they see a regular flow of K-crazy clients day in and day out. Though I came up with my own combination of parts after way too much internet research, Song offered advice and insight based on his own builds and experience throughout the entire process. SCM had the bottom end swap done in just two days flat.
Dyno day - Church Automotive Testing (C.A.T.)
The Church dyno facility is a busy one. Morning, noon, and often nights are filled with tuning clientele. We were able to get a mid-afternoon appointment with Daniel Butler, a guy that's tuned more K-series engines than he can possibly remember. His vast experience with K24/K20 combos made him the perfect choice for tuning duties.
On the Dynapack, Butler spent some time mapping out a starting point. After the initial run, the car was sounding better and better with each blast. About an hour later, Butler was inching ever closer to the 300hp mark, but made a few changes that saw a slight decrease in peak horsepower. The trade-off being an increase in useable torque.
Trying to write about how the car feels now is rather difficult. Yes, the difference is night and day, with real torque that you can feel from the bottom, all the way up to the top. But it's the overall feel of the engine; snappy, light, rev happy, it just wants to "go." Downshifting on the freeway is a thing of the past, requiring only that I apply a little gas in Sixth gear to scoot right around anyone in front of me. Exiting a corner is a whole new world as the car tears through Second and Third gear. Any thoughts of opting for a more aggressive final drive were quickly out the window, as the car literally tears ass through the factory issued gearing, and in quick fashion. Mission accomplished? Absolutely. The dyno sheet and the fun I've had behind the wheel ever since would attest to that ...