Honda B vs K Series: Which is Right for Your Build?

Judging from internet forum wars, riddled with fiery posts and personal attacks, the choice between a Honda B or K series engine is more a religious decision than one based on fact or mechanical superiority. Even within the brand, engine loyalties abound. However, when the smoke from the forum flames clears, each one of these capable engines has a unique set of pros and cons to weigh.

The Original B-Series

engine 005

The B series engine garnered a cult like following in it’s 12-year production run.

The first consideration that needs to be made is cash. Few automotive enthusiasts have access to a money tree or the limitless financial resources to throw stacks of cash at a project. For that reason the B series is a budget friendly choice.

While the B is no sissy, with racing examples regular eclipsing the 1,000 horsepower mark and street builds sneaking up on unsuspecting V8s, it is still a baby in the eyes of the aftermarket: their baby.

First introduced to the US in 1989, the B-series has been the go-to platform of Honda tuners for 25 years. In that time, aftermarket companies have been building, testing, and selling parts for the platform in droves; making them plentiful, time-tested and, most importantly, very affordable.

If budget is a major concern in a planned build, the B series certainly shines. And, thanks to a 12-year production run, there are plenty of B-series cores ripe for the picking on your Craigslist locality of choice. Most examples — especially the B16s and B18A series — can be picked up for a few hundred bucks, but rarer trims such as the B18Cs and B18C5s still command primo coin.

“They just came in so many different platforms,” said Mike Laskey of Laskey Racing. In a few years, as more and more K-powered vehicles find their way into junkyards across the country, core prices will drop even further making this engine more accessible to tuners.

When pricing out a project, it is important to look at the big picture. “The B series will ultimately be cheaper to swap into an older chassis,” said John Rodcharoen of Golden Eagle Manufacturing, a company that has aided in Honda performance since before the birth of the B series.

K24

This K24 engine features an 87mm bore and 99mm stroke, huge for any Honda platform.

Now, to say the K-series is outlandishly expensive to build or that it doesn’t have its share of aftermarket love would be a lie. The shorter and more recent

“There is no fabrication needed to adapt it to the chassis.” While there are swap kits available for K engines, such as those offered for ’92-’00 Civics, and ’94-’01 Integras by Hybrid Racing, they are an extra expense ($1200 for Hybrid Racing’s kit). Retrofitting a K engine certainly requires much more involvement than using a B series engine, which many older Honda platforms came with from the factory in either USDM or JDM iterations.

Size Matters … When NA

Sleeved B series

Even with aftermarket sleeves, the displacement capacity of the B series is limited by the bore spacing.

“There is no replacement for displacement”, says Laskey, Rodcharoen and about every other person we talked to. And, this statement rings especially true in the world of naturally aspirated power. Due to this fact, the K series engines have a solid advantage over the Bs.

With a square 86mm x 86mm bore and stroke, as delivered from Honda, the smallest variant of the K20 series still puts a .2-.4 liter lead on all of the B-series line, save for the B20. In the world of Honda four-cylinders, even the smaller K is big; but, they get even bigger.

Throw a K24 bottom end into the mix (87mm bore x 99mm stroke) and there is simply no way the B-series can go toe-to-toe with the K’s displacement.

“Even with an aftermarket sleeve bored to 87 mm and a 100-105mm stroker crank you are only getting about 2.3 liters from a B, and that’s stupid-big status,” said Rodcharoen

Displacement, however, is only half the battle. A big motor that can’t breath is a still a turd. That must have been have been the rally cry of Honda engineers during the K’s development because they made damn sure the K platform could breathe.

This B-series block is being prepped with cylinder Sleeves from Golden Eagle Manufacturing for big boost and insane horsepower.

The cylinder heads on the performance variants of the K-series engines are some of the best the company has ever designed. With extremely high-flow ports, 33mm intake valves (2mm up from the B series) and full-roller valvetrains – it’s a good thing there is no shortage of atmosphere.

Laskey's Bad B Series

Mike Laskey doesn’t just build badass motors, he races them too. Team Laskey is currently building this 2000 Civic SI powered with a turbocharged and intercoolered B18C engine. The engine has been prepped with Benson sleeves, CP pistons and Carrillo rods. Portflow handled the head-porting duties while Supertech valvetrain actuates the valves. Laskey estimates the engine’s output in the 1,100 horsepower range.

K series engines have routinely cracked the 300 hp barrier naturally aspirated and, if all-out NA performance is the goal, it’s difficult to compile a case against the K platform.

“The K series is better by a long shot: the head flows higher CFM’s it has roller rockers and bigger displacement,” said Rodcharoen.

Boost Supremacy

In the realm of forced induction, the gap between the K-series and B-series narrows.

While the K-series does pack the previously mentioned, higher-flowing cylinder head and displacement bump, the B easily overcomes those perks with boost.

B and K engines can take quite a bit of abuse before reaching there limits but both will need sleeving, uprated fasteners, pistons and connecting rods when extremely high boost and power numbers are planned.

With that being said, there is some dissent among top Honda builders about horsepower limitations of each of these engines in stock form.

Rodcharoen advises that the stock sleeves be replaced when approaching the 300 horsepower level on B series engines. While he admits that he has seen engines eclipse this number without sleeving, his experience suggests they are on borrowed time.

The K-series valvetrain is a huge improvement over the B's in factory trim but, retrofit rollers like these Ferrea units are available for the B series.

“While both B and K blocks are cast with cast iron sleeves from the factory, the K has more aluminum cast surrounding the can which helps with the cylinder strength,” said Sean Ragains of ERL Performance, the company behind the Super Deck and the builder of many quadruple horsepower Honda engines.

“They both can handle a reasonable amount of cylinder pressure,  but where we see an issue is when there is either detonation present or a power adder is used which pushes it beyond its limit.”

When it comes to pistons, both engines are issued with cast slugs and any serious builder will recommend a forging in a turbo setup. As far as one of these engines having the absolute advantage when it comes to turbocharging, it is difficult to say, but the B series can certainly holds its own.

“A bigger K-series motor is going to spool the turbo a little quicker,” says Laskey “But, a lot of the faster turbo cars tend to still be B-series motors.”

Another important advantage is in combustion chamber sealing, something the B-series engines do well. “Their is an advantage to sealing strength on [B series] cylinder heads for heavily boosted applications due to the smaller bore and spacing which allows for closer head bolt location relative to the cylinder,” said Ragains.

The K series (left) has more material around the cylinder sleeves than the B series (right). This makes for a stronger block from the factory.

Long Block Talk

IMAG1496

The presence of timing gears makes it easy to identify a B engine from a K.

The B- and K-series engines both have thoroughly over-engineered blocks that can live with gobs more horsepower than Honda ever intended. But, when compared side-by-side, the K-series is clearly the more innovative and perfected platform — and why wouldn’t it be? It’s ten years the junior and the natural evolution of the B-series motor. First up on the “what’s changed” list is the addition of a timing chain.

Honda tuners have had a long while to become familiar with timing belts as Honda used them nearly universally right up until the debut of the F20c engine in the Honda S2000. Shortly after, the K-series was released with — yup, you guessed it — a timing chain.

While timing belts have been a longstanding staple of lightweight reliability and are quite aesthetically appealing, means to keep the valvetrain humming in tune, the timing chain is a more durable means to do the job. The chains used on the K series do an admirable job of preventing the pistons from getting intimate with the valves, especially so when I-VTEC comes into play. There are some issues with the K’s timing chain tensioner though. Hybrid Racing makes an upgraded unit but according to Rodcharoen, making sure to replace the stock tensioner with a fresh unit (especially when the short block has high mileage) is usually sufficient.

Spun cam bearing

Here is an example of a B-series head that spun a cam bearing. The cam bore is heavily scored and the head is now junk.

Also on the renovation list during the K-series design stage was the valvetrain. Gone are B’s pad style rockers and in their place are a set of roller units. The roller wheels ride directly on the camshaft lobe, reducing friction to create a more rev happy engine.

Honda also changed the manner in which the valvetrain attaches to the head. In the B-series, the lower bearing perch is machined into the head with the upper cap bolted on top. The setup works fine, but if a cam were ever to spin a bearing or have an issue, the entire cylinder head is now junk. The valvetrain in the K bolts to the head and is entirely removable and replaceable. “It’s possible to make a repair at the track if you hurt the cam,” said Laskey.

Gizmos and Gadgetry

A lot like the completely outdated computer you bought last Wednesday, the B series has several dated components. And, due to its decade of technology improvements over the B, the K series engine pack some extra, techie hardware.

The B is old technology,” But I’m a diehard B series for life. – John Rodcharoen

While many B engines rock Honda’s famous (and at the time revolutionary) VTEC valvetrain, several of the K-series engines come standard with Honda’s new-age I-VTEC system. The difference lies in I-VTEC’s cam phasing abilities. While VTEC allows the engine to mechanically engage a different, more aggressive cam profile at a predetermined RPM, I-VTEC can also actively advance or retard the camshaft plus or minus 50 degrees.

The ignition system is another segment that was substantially revamped in the K engines. Gone is the antiquated distributor, spark plug wires and single coil. In its place, a modern coil-on-plug ignition system that delivers more powerful, precisely metered sparks with impeccable timing accuracy. The beauty of the computer controlled ignition is that spark advance can be metered out at the perfect time. For this reason K series engines are issued with much higher compression ratios from the factory (as high as 11.7:1 in JDM K20a engines) than earlier distributor based B-series engines.

Will it fit?

swap kit

This swap kit from Hybrid Racing makes dropping a K series engine into an older chassis easy.

Swapping a K-series motor into your older chassis is a lot easier today than it was even five years ago, but still presents its own set of difficulties. Part of this difficulty stems from the engines rotated orientation. Unlike the B series, the K spins clockwise. This put the exhaust ports facing the firewall and the intake ports toward the front of the car.

The new orientation makes exhaust routing much easier but the engine will require aftermarket mounts to bolt in to an older chassis. Aftermarket axles that adapt the K-series transaxle to applicable Honda knuckles will also be required. Because there are so many variables for each chassis, we won’t go into full detail on engine swaps. But we will make the case that the K-series is a more involved swap than the B, which can often be installed through the use of factory components like axles and mounts.

A lot of us guys have a hard-on for the B series because it’s what we grew up with. But that shouldn’t take away from the merit of the K series. – Mike Laskey

To B or not to B

So at the culmination of this article is it clear which engine you should build? Of course not! Both are engineering marvels capable of producing mythical levels of horsepower per liter. A built version of a B or K engine promises to be indiscriminately fun and fast. Yes, the K series tips the scales in its favor in virtually every mechanical aspect but the B series is such an affordable, available and beloved platform that it is absolutely unfair to rule it out. Better armed with a little knowledge about each of these platforms, the choice is still yours to make.

This 3-main girdle used on some B series blocks adds strength but is not quite as strong as the full girdle of the K series.

About the author

Evan Perkins

Evan Perkins is a seasoned automotive journalist with a passion for road racing. Evan has logged seat time in more cars than he can count and has a deep-seeded love for all genres of the motoring world.
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