K24 Vtec V.s. G23 Vtec

K24 VTEC V.S. G23 VTEC - Tech Knowledge
Move Over K24, The Frankenstein G23 Packs The Same Punch At Less Than 1/4th The Cost
By Luke Munnell
Photography by Somya Siva, Chris Bolin

If you're reading this, chances are you've owned a swapped Honda or two in your day. If not, you probably want one. But where to start? B18A/B engines offer two cams and 1.8 liters of displacement-but also a lackluster cylinder head. B16As are cheap and offer VTEC... but are also old and relatively small. The venerable B18C is becomming increasingly more expensive and scarce, not to mention overshadowed by the K20A's i-VTEC, aggressive cams, roller rockers, and extra .2 liters of displacement. Which sound great, until you factor in its $5K price tag. And there's the boss of them all: the K24. One and a half times the size of a B16, 200 hp out of the box, and the potential to make much more power than any of the afore-mentioned options. Pull one out of a TSX, or build a K20/24 hybrid - either way, if the thought of dropping $5,000 on a K20 swap made you cringe, forget this option right now.

But what about Honda's "big block" of yesterday, the H22A? DOHC, VTEC, 2.2L of displacement, and 190+ hp all for a third of the K-series' price. Not a bad deal, apart from its fiber-reinforced metal (FRM) cylinder walls that make over-boring impossible and don't get along with aftermarket pistons. So what's an economical (read: broke), but mechanically inclined Honda owner to do? If you're Bolisbuilt's Chris Bolin, you roll all the above engines into one 2.3L, 250 hp, DOHC VTEC monster, name it the "G23 VTEC", and do it all for less than you'd spend on any of the others.

01. "I was looking for a reliable engine I could swap in my EF, make big all-motor power with, and just drive every day," Chris tells us, "A K-series would've been great, but they were too expensive. And I wanted something bgger than a GSR or B20 VTEC," he continues, "So I started thinking about swapping in a stock H22A." But then he read about a Honda-tech member's write-up of an F23/H23 "Frankenstein" project. "This guy had successfully mated a non-VTEC H23 head to an F23 block," he explains, "and my friend was selling an H22A long block with a spun rod bearing for $200, so I figured why not try it with VTEC? I bought an F23 short block for $100 and got to work."

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02. Despite many similarities between Honda's F- and H-series engines, each offers advantages that the other lacks. The H22A brags a higher-flowing, DOHC VTEC cylinder head. The F23, .1 liter more displacement and iron cylinders. What's more, the F23 block features 55mm main bearing journals, while early H22As measure only 50mm, and the F23's girdle is much bigger than most Honda engines. The F23 is the only engine out of the bunch with a stroke as long as 97mm, and an 86mm bore. Because of this, conventional wisdom held that F23 pistons and rods had to be kept with the block when switching heads, but the higher combustion chamber of the H22 head brought compression down to a low 8.8:1 - great for boosted applications, but Chris wasn't after that. Since the F23's piston specs nearly mirror the K20's, and that both engines share a floating rod design, Chris found that K20 pistons would fit on stock F23 rods, inside a stock-bore F23 block. And they'd bump compression to 11.5:1 when used with the H22A head. "The valve reliefs in the K20 pistons fit the H22 intake exhaust valves perfectly," he adds, "it's like Honda took a good look at the F23 when they designed the K-series."

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03. No major machine work was needed to bring everything together, but the H22 head uses eight ports to drain oil back into its block; the F23 block uses only six. All of the F's drain ports match up with the H22 head, but the remaining two Chris had to block off with DIY plugs, consisting of bolts driven into the head and then grinded flush. There was also a slight difference in external water pipe routing between the F and the H, which Chris solved with some creative use of a welder and some scavenged pipe. "But a piece of silicone radiator hose and clamps would do the trick," he notes.

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04. It is often said that timing is everything. That goes double for an en engine made of two halves of different engines. Since the H22A head was used, Chris reasoned he'd adapt the F23 block components as needed. The F23 water pump was pulled apart from its gear, and pressed into an H22 unit. The H22 crank cog and F23 pulley were used, and top dead center (TDC) was found the old-fashioned way, by inserting a TDC gauge into the number Two or Four cylinders and marking on the F23 block where the crank pulley pointed at their lowest points, then lining the H22 cam gears up at their stock points. An H22 timing belt was wrapped around the mix and tensioned using OE F23 equipment. The H22 distributor was retained, the EF wiring harness was modified to work with the new engine, and the whole car was converted to OBD 1 and synched to a Crome-chipped P28 ECU. "But the stock H22A P13 ECU could also be used," he advises, "and initial timing should be about 16 degrees before TDC at a 1,100-rpm idle."

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05. Finally, there was the driveline. Just how does one get a K20-infused, Prelude/Accord hybrid engine to power an EF Civic hatch, anyway? It's easier than one might think. Since the chassis originally used a cable-actuated transmission, Chris decided to start with a B16A S1 trans., coupled to the F23 block using QSD's H2B adapter kit. Consisting of a trans. adapter plate, mount adapter, flywheel spacer, and half-shaft adapter, all Chris needed to add were Hasport B-series mounts for the EF Civic all around, a stock B-series clutch, flywheel and half-shaft, a JDM Civic SiR linkage (or a Hasport one), and DA Integra axles. The stock EF throttle cable was adapted to fit the new engine.

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06. With the engine assembled, bolted up to its trans and dropped into its new EF engine bay, it appeared that Chris was on the homestretch with his project. Until he discovered a new set of hurdles to clear: fitment. "If you've ever looked at a Prelude engine bay from the side," he notes, "you'll see that the H22A tilts back toward the firewall, allowing better clearance for the hood. The H2B kit doesn't give the F23 block this lean, so it sits way higher in a Civic engine bay than a B- or an H-series engine, especially in the EF bay." Chris not only had to notch his hood's skeleton for clearance, but also prop the back of it up nearly two inches. He used an Innovative Mounts alternator re-locater bracket to buy a little more room, but still had to bang out the frame rail with a sledge hammer to allow clearance for the crank and alternator pulleys. The stock H22 fuel lines and filter were all retained, but an intake and header had to be custom-made, and the stock exhaust had to be modified. "But the OE H22A intake and header could suffice with a little work," says Chris.

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07. With the car up and running, Chris could've stopped where he did, with a 2.3L hybrid mill boasting K-series power and torque for a fraction of the price... but why not spend a little more to make it even faster? In researching his build, Chris learned that, for nearly the same coin as used OE K20 pistons, off-the-shelf Wiseco K20 pistons could offer even higher compression-12.8:1-and their valve reliefs could accommodate the increased lift and duration of much more aggressive cams... like the used Skunk2 Pro 3 cams and cam gears he found on eBay for $500, that he coupled with Supertech dual valve springs and titanium retainers for a few bucks more. To help the cams reach their fullest potential, Chris replaced his homemade intake with a set of 52mm TWM ITBs. A Kaizenspeed balance shaft removal kit frees up a few additional ponies by reducing rotational mass. And since the whole engine was now making more power, Chris saw it fit to strengthen its driveline, while removing a little more rotational mass, by ditching his OE B-series clutch and flywheel with Clutchmasters FX500 and ACT Prolite replacements. The result: 248.6 whp and 181.2 lb-ft of torque, as measured and tuned by the Latrobe, Pa. based HybriDynamics crew.

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08. "It all worked out better than I expected," Chris confesses at the end of it all. "It's a great all-around motor; lots of power, loads of torque, and built with easy-to-find parts. It goes to show you don't need a 'K' to make a lot of 'HP'." But Chris cautions that not everyone should embark on a G23 build. "If you've got the tools and a garage, and know your way around an engine, by all means-go for it," he advises, "But if you're expecting it all to just snap together... better let a pro handle it." Words to live by. Chris has had his EF out to the strip a few times since completing its build. It's gone low 12's with a full interior and street tires, and Chris expects to be deep into the 11's after a head port, tuning, and possible over-bore. "The best part of it all," he says, "is the look of confusion on people's faces when you lift the hood. They don't know what the hell it is!"

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The Bare Bones G23
Parts You'll Need To Build One On The Cheap
200+ WHP

F23A COMPLETE SHORT BLOCK (USED) BLOCK, RODS, CRANK,
OIL PAN, OIL AND WATER PUMP, CRANK TIMING COG AND PULLEY,
EXTERNAL WATER LINES, SENSORS, ETC. $200
H22A COMPLETE HEAD (USED)ASSEMBLED HEAD AND VALVE COVER,
INTAKE MANIFOLD AND THROTTLE BODY, DISTRIBUTOR,
FUEL RAIL AND LINES, SENSORS, HEADER, ETC. $300
H22A CRANKSHAFT TIMING COG (USED) $25
H22A TIMING BELT (NEW) $50
H22A HEAD STUDS (NEW) $50
H22A HEAD GASKET (NEW) $50
K20A OEM PISTONS, JDM OR USDM TYPE-S (USED) $100
H22A P13 ECU (USED) $75
B-SERIES TRANSMISSION OF CHOICE (USED) $300
STAINLESS STEEL BOLTS FOR OIL DRAIN BLOCKING (NEW) $1
B-SERIES CLUTCH AND FLYWHEEL (USED) $100
H22 WATER PUMP (USED) $10
K20 PISTON RINGS, ACL F23 BEARINGS, OE H22A GASKET SET (NEW) $200
DA INTEGRA AXLES (USED) $50
FABRICATION (MOUNTS, LINKAGE, INTAKE, EXHAUST) $300
TOTAL $1,811


The P.I.M.P. Steeze
WANNA REALLY KICK SOME ASS?
260+ WHP

BARE BONES G23 VTEC (PREVIOUS TABLE) $1,811
SIX SIGMA RACING HEADER (NEW) $800
CAMS AND CAM GEARS (USED) $500
SUPER TECH DUAL VALVE SPRINGS AND TITANIUM RETAINERS (NEW) $315
QSD H2B ADAPTER KIT (NEW) $750
KAIZENSPEED BALANCE SHAFT REMOVAL KIT (NEW) $150
ACT PROLITE FLYWHEEL (NEW) $260
CLUTCHMASTERS FX500 CLUTCH (NEW) $310
TWM INDIVIDUAL THROTTLE BODIES (NEW) $1,500
CROME TUNING $300
TOTAL $6,696

Comparison
Check Out Other Swap Options

B16A SIR 158 HP, 111 LB-FT $2,225
H22A PRELUDE 195 HP, 156 LB-FT $2,375
B18A/B LS 140 HP, 121 LB-FT $3,025
B18C GSR 170 HP, 128 LB-FT $4,025
K20A TYPE-S 198 HP, 142 LB-FT $6,275
K24A TSX 200 HP, 166 LB-FT $7,425

I just made a mess on my keyboard... (drool you sick pervs, drool)

This is an awesome post, thank you for posting it. I do have a question though, what is a "crankshaft cog"? I've never heard of the term "cog" before. (Edit: it's the gear right?)

The toothed pulley that drives the timing belt. A cog is a gear.

it looks better posted than in the mag,
there has to be a better way to plug the oil holes in the head than "but the remaining two Chris had to block off with DIY plugs, consisting of bolts driven into the head and then grinded flush."

Actually thats a pretty good method honestly. Thats basically what honda did for the oil control orifice in the vtec heads that needs to be removed when doing a minime.

it looks better posted than in the mag,
there has to be a better way to plug the oil holes in the head than "but the remaining two Chris had to block off with DIY plugs, consisting of bolts driven into the head and then grinded flush."

yeah, you could spend hundreds having it welded up...

I don't necessarily agree with using bolts to fill the holes, b/c of the heat-exchange differences between the steel bolt and the aluminum head... it might loosen or leak eventually.

I would say more likely to thread the oil-return hole the right way, and thread an aluminum rod, then thread them together with loc-tite or something... that way they'd be less likely to develop a leak.

Potential argument - "But the holes aren't perfectly round!"

Basic answer - "Great - thread the larger part of the hole, put in your rod, then drill the rod to match the rest of the hole, and run the tap through your new hole. Thread another piece of rod into that hole, keep doing this until you're sealed."

yeah, you could spend hundreds having it welded up...

I don't necessarily agree with using bolts to fill the holes, b/c of the heat-exchange differences between the steel bolt and the aluminum head... it might loosen or leak eventually.

I would say more likely to thread the oil-return hole the right way, and thread an aluminum rod, then thread them together with loc-tite or something... that way they'd be less likely to develop a leak.

Potential argument - "But the holes aren't perfectly round!"

Basic answer - "Great - thread the larger part of the hole, put in your rod, then drill the rod to match the rest of the hole, and run the tap through your new hole. Thread another piece of rod into that hole, keep doing this until you're sealed."


It's the same thing as plugging the oil line in a ls/vtec conversion. They cannot back out as they will hit the headgasket.

Yes, he could have tapped it, and plugged it with the 1/8th npt plug. Why make it harder than it has to be?

It's the same thing as plugging the oil line in a ls/vtec conversion. They cannot back out as they will hit the headgasket.

Yes, he could have tapped it, and plugged it with the 1/8th npt plug. Why make it harder than it has to be?
Except in the case with this engine, it will hit the block deck, and not the head gasket, and I'd personally still prefer that it be threaded and sealed. Also - using steel against aluminum in a part that isn't holding/held by anything isn't necessarily "good" engineering, considering that the alloy head will heat up and expand MUCH faster than the steel, it could eventually leak. Steel also work hardens faster than aluminum does, so that will also cause a leak.

Frankly, I'd rather just over-do it the first time than have to do it again, even 50,000 miles later. To me, it's not reliable if I have to fix it sooner than the natural life of the engine would have been. Obviously, a modified engine probably won't last more than about 100,000 miles before needing a rebuild due to performance loss - but I shouldn't have to fix the head plug again at that point.

But I digress - It was a simple suggestion - whether you (or anyone else) choose to follow it is entirely at your (their) discretion.

I'll go back to my Minivan now...

Here's a thread on Honda-Tech, from the person who did this.
http://www.honda-tech.com/showthread.php?t=2252451

I briefly read through it late last night after I read this thread (it was actually linked on the from page of H-T strangely enough). But I recall him saying that he put the bolt in and used some kind of Honda sealant (not Hondabond) to ensure it stayed on there, if I'm remembering correctly (it was late). Someone in the thread also mentioned having to figure out a way create a return line for those 2 oil ports, since they will be closed, but apparently are still needed :confused:

I would guess (without reading it) that it said something to the extent of "Honda wouldn't have put them there if they weren't necessary, so you should find a way to port them back to the block, rather than blocking them entirely."

Or "If you don't port the oil back to the block, oil will pool in the area above those ports and cause drag issues."

I doubt either of which will become a problem, but people seem to use the "OEM did it, so it must be right" complaint a lot when they don't understand how something works (or doesn't work).

EDIT - Just read it - the concern was b/c of Vtec, that starvation would occur, since Honda added the extra oil passages for the Vtec on both sides of the engine, instead of just the intake side. Bolis doesn't seem to care.

So, how do you explain the use of steel head studs, steel studs for both intake and exhaust manifolds, steel cam cap bolts, steel alternator bolts, steel vtec bolts, steel water pump bolts, steel crank cap bolts, steel oil pump bolts...

All unreliable?

My old B20/vtec motor just surpassed 80k miles in my first hatch. Still runs pretty damn good, aside from a leaking oil pan gasket.

We're not talking aerospace tolerances here, just simple automotive junk.
I explain it simply - None of those things are holding back engine blood, and they're all threaded.

I also just read that the stainless steel bolts he used were press fit, and he used ultra-flange to seal them. This may make a difference, I'm not sure - fact is, I still wouldn't do it with my own setup.

I explain it simply - None of those things are holding back engine blood, and they're all threaded.




I caught that after I posted, that's why I removed my post. :rolleyes:

Rather than add my other points of disagreement. I left it at that.

kris - fair enough.

looks lie fun :)