Importing a Honda H23 Engine for Your Next High-Revving VTEC Swap

Finding an H23 Engine for Your Honda Build

If you're building a high-performance Honda civic, chances are you've looked into swapping in Honda's powerful H23 engine. The H23 is a 2.3L 4-cylinder engine that Honda produced from 1991-1997 for use in Preludes and Accords. With VTEC technology allowing variable cam timing, these engines can put out an impressive amount of naturally-aspirated horsepower while still being reliable.

However, finding an H23 engine for sale can be tricky these days. Since they haven't been in production for over 25 years, good condition H23 engines are getting harder to find. But don't worry, here's what you need to know about buying an H23 motor for your Honda swap.

Where To Find an H23 Engine

The best place to find an H23 engine is from online JDM importers. Since H23 engines were never sold in American-spec Honda models, you'll need to import one from Japan. There are a handful of reputable online importers that source high-quality, low-mileage JDM Honda engines.

When searching for an H23, you'll want to look out for importers who specialize in Honda and test all their inventory. This helps ensure you get an engine that is in good health and hasn't been tampered with. Expect to pay anywhere from $1,000 to $3,000 depending on exact specifications and included accessories.

What to Look for When Buying

There are a few key things to inspect before purchasing an imported H23 engine:

• Check mileage - lower miles means less wear
• Ensure it starts and runs smoothly with good compression
• No leaks, damaged sensors, or excessive play in moving parts
• Comes with intake, wiring harness, ECU, etc.

While shopping for an H23, it helps to understand exactly what engines Honda offered as well. The H23A1 is the rarest USDM version making about 170 hp. But most imported engines are H23A VTEC motors making 197 hp.

Why Choose the H23 for Your Swap?

If you're deciding between Honda engine swaps, the H23 has some compelling advantages. Here's why it may be the optimal choice over B-Series or K-Series alternatives:

High Power Naturally Aspirated

With 197 hp on tap in stock form, an H23 engine offers impressive peak power without forced induction. This high specific output allows builds making 400+ horsepower NA before needing a turbo or supercharger. Plus the linear power delivery of NA engines is preferred for track driving.

Weight Savings Over B-Series

Weighing under 350 lbs fully dressed, the H23 shaves over 75 lbs of mass compared to a B20 or B18C engine. This improved front-to-rear weight distribution helps handling. And the lightweight engine reduces load on other drivetrain components.

Ideal for High-RPM Applications

The H-Series engines in Preludes were designed for high-RPM power. With aggressive cams and 7800+ rpm redlines from the factory, H23s love to spin into the upper limits. This character makes them perfectly suited for road course and canyon driving, where keeping the engine on boil yields faster lap times.

H23 Engine Bay Swap Considerations

While the H23 may seem too large for engine bays designed for 1.5-1.8L motors, crafty builders have stuffed them into all generations of Civics along with Integras and Del Sols. Here's what you need to know:

ECU and Wiring

A properly functioning ECU and wiring harness is crucial for getting an H23 swap running optimally. This may require custom wiring work. So plan out where you'll route all necessary connections from VTEC solenoids, cam and crank sensors, etc. during the swap process.

Motor Mounts

Since the H-Series engine has different mounting points than B and K-Series alternatives, you'll need motor mount adapters to correctly align it within the engine bay. Be sure to secure mounts sturdily as the torque of high-revving H23s can tear through weaker mounts. Consider solid or reinforced urethane mounts for durability.

Axles and Drivetrain Compatibility

While transmission compatibility requires assessment once you choose a donor car, the H23 bolt pattern matches K-Series engines. So K-Series axles can be retained for simpler integration. Just ensure your axles can handle the increased torque expected from such a powerful engine.

Is the H23 Right For You?

If you love the high-winding nature of VTEC engines and want maximum power without forced induction, the H23 is an appealing Honda swap choice. With ample availability thanks to importers, there are still opportunities to give this venerable engine a new lease on life.

Just carefully inspect any imported engine, shop with trustworthy suppliers, and properly plan out your swap process. Follow these tips and your H23 Civic build will be singing at redline in no time!

FAQs

What kind of power can I expect from an H23 engine?

In stock form, H23A VTEC engines make about 197 horsepower. With light bolt-on modifications like intake, header, camshafts, etc. you can reliably achieve over 250 horsepower NA. Further built engines with aggressive tuning can reach up to 400hp or more still naturally aspirated before forced induction is required.

What transmission options work with an H23 swap?

The H23 bolt pattern matches K-Series engines, so any transmission that works with K-swaps like K20A, TSX CD7, etc will bolt up. For more budget friendly options, the H23 mates well with B and D series transmissions found in Civics and Integras when using an adapter plate.

Do I need to upgrade other drivetrain components with an H23?

As with most swaps over 150hp, upgrading axles is recommended if running the stock units. A good minimum is to use RSX type S or similar axles rated to handle upwards of 200 ft-lbs torque. Adding a limited slip differential and stronger half shafts is also a good idea to optimize traction.

What extra modifications does an H23 swap require?

Expect to fabricate custom engine mounts to correctly align the H23 within your engine bay. A standalone ECU or rewiring of the factory unit is also typically needed to integrate the VTEC and emissions systems properly. Finally, a custom stainless exhaust that maximizes airflow helps unlock the full potential of these high-revving engines.