Building the Naturally Aspirated Honda K Engine Part 3, Assembling the Engine


The Dailey dry-sump system is very integrated and cleanly designed, with the pan serving as the bracketry as well. Also, an ATI balancer is part of the dry-sump system.

The ATI balancer is a custom tuned, heavy duty, elastomeric balancer that is designed to attenuate vibrations at higher rpm- not just rpm where NVH is an issue.  The ATI balancer is SFI approved and will possibly improve bearing and crank life for continual high rpm use.

One issue when building a hybrid of a K24 Z7 and a K20Z3 is that the front covers are slightly different and won’t seal in the front right corner area. We fixed this by cutting and shaping a piece of aluminum and welding it onto the K24 front cover. Care must be taken to ensure a proper seal.


Since our engine is making a lot more power, we used the OEM injectors off of a K23A1 Turbocharged RDX engine. These flow 410cc/min- up from the stock 310cc/min. This should be more than adequate for our NA engine.


To complement our other parts and camshafts, we decided to use an RBC intake manifold. The RBC intake manifold is the stock Honda intake manifold for the Euro Accord Type-R and our Civic Si from 2006.

The RBC manifold really shines on moderately modified 2.4-liter engines like ours, with its larger plenum and bigger in diameter, shorter runners. The RBC can even out power many race-type aftermarket manifolds. 

We had to modify the RBC manifold to fit on our K20Z3 head. It was not too difficult, and the instructions to do it can be found here.


We topped off our RBC manifold with an Acura ZDX throttle body. The ZDX throttle body is off of a 3.7 liter V6 and is a whopping 70mm inch diameter- compared to the stock 64mm.

We used a PRL Motorsports throttle body adaptor to bolt it on to the RBC manifold.


For a lightweight car like the Atom, we wanted a super light, low inertia clutch. We chose ACT’s twin disc racing clutch.

With a featherlight weight of 17.2 lbs for the ENTIRE assembly and a small 7.25″ diameter, the ACT twin disc is not only much lighter than even a lightweight high-performance conventional clutch, but it is much lower in inertia as well for more instantaneous throttle response.

The ACT Twin Disc has two 7.25 inch sintered iron discs sandwiched between two floaters. The clutch body is a very open, six-post design, which is better for cooling and dust ejection.

With a lot of friction area, a twin disc can offer a lot of torque capacity without having to increase the pressure plate clamp load as much. This is easy on the clutch pedal and the engine’s thrust bearing. The ACT Twin Disc can hold 770 ft/lbs, which is 314% better than stock.

With two discs, the size of the disc can also be reduced for lower inertia as well for fast revving and a quick response. The ACT clutch is SFI 1.2 certified and has a one year warranty to boot!


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