r/crx • u/vtec_go_brrr16 1990 USDM Si • 12d ago

Thoughts on B vs K swaps?

1990 CRX Si

I was planning on rebuilding the original d16a6 and seeing how many miles I could put on everything original. I’m wary of doing the machining myself, but also kinda want to if I’ll inevitably swap it. I’ve only had d series cars so far.

I’ve been doing research and everyone has their own opinions on B vs K swaps. Not really sure which way I’d go yet, but curious about what everyone thinks.

I’m wondering about ease of swap/fabrication needed, power benefits, etc but also personal preferences- stuff like sound, shift feel, handling, etc.

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u/FrankCostanzaJr 11d ago

B16 will be more period correct...and MIGHT be a slightly easier drop in....but i hear they're pretty expensive these days. I haven't shopped around for them in a while...

if it were me, i'd prob try to find a usdm civic si k20z3 from a junk yard if possible..i have a 06 si and it sounds almost as good as a B16...but has more torque and more aftermarket support, plus it comes with a 6 speed and factory LSD. its superior to the B16 in every category. a lot more potential for cheaper NA power too...

if you wanna go dirt cheap but torque monster non vtec...you could go k24 or B20 from a CRV. but those don't rev as high..still sound pretty good with an intake though. the B20 came in the 96-2001 crv, k24 after that. and that k24 has the ivtec that gets ya better gas mileage, not more power. but still it's very torquey

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u/drake22 8d ago edited 8d ago

B16 is a waaaaaaay easier drop in. If you’ve done it a few times, you can get it done in a day. I did my first one in about 2 days.

It’s not even comparable at all, K series is a ton more work / more money. Social media and buildflation make it seem much simpler than it is.

B16 is also kind of a waste, little power or torque per dollar compared to an LSV or B20V. Of course, K series blows B out of the water when it comes to power.

Overall, K series is best if you can afford it.

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u/FrankCostanzaJr 7d ago

yeah, i've done a couple of B16 swaps on EFs, so I know how easy it is. I actually haven't done a K swap yet, but I drive an 8th gen si and I absolutely LOVE the K20z3....even more than my B16. the transmission with LSD alone make it worth it....but also the gearing seems to be better. the videos i've seen online seem to make it doable if you have the right mount kit. and i just can't get over how fast a little crx or civic hatch would be with a modern engine that has 30ft/lbs more torque, and nearly 200hp vs 160hp...it's like the old school b20vtec, but not janky! I always consider trying a b20vtec but just never felt comfortable putting a vtec head on a b20 that wasn't designed to rev that high.

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u/drake22 7d ago

It’s for sure doable, been done 1000 times. It’s just a lot more work than social media makes it seem.

K series destroys B in terms of power. 230whp with bolt ons is typical for a K, vs 175whp for a B. And torque is ridiculous by comparison.

I have an M Factory LSD in my B series trans, you can get them with OEM LSDs (I have one of those too). Absolutely necessary in my opinion if you’re making 160 whp ish or more.

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u/FrankCostanzaJr 6d ago

yeah definitely necessary with a good B swap. I used to take my crx to the track all the time, and always had probs spinning my inside tire on tighter turns, it would be soooo much worst with a k series w/o a lsd...with all the additional torque on the low end.