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Honda civic CX to DX head swap

Alright, so I have a 5-spd 94 cx hatch and I just put a 16v 94’ dx head on the block. I have also converted the throttle body and injectors over to dx spec as well. However, I still have the stock CX exhaust mani on the block.

The problem I am having is that when I drive it, I am not getting much power. It struggles to get up into the higher RPMs when in gear. It revs up fine in nuetral, and my tranny is is good shape, but is my problem with the sluggishness my exhaust mani or the injectors or potentially something else?

Did not know you could do that swap, but have you checked the cats, especially the warmup cat. If the warmup cat is built into the exhaust manifold, it maybe hard to check unless you remove it completely.

well, the b7 and b8 pistons are the same except for the valve reliefs (and that changed over to all of them having the same reliefs sometime in 93/94, so you’re probably fine there), which won’t effect the engine actually working, so with the head swap, OP basically got himself a full DX engine.

Did you swap ECU’s as well? the CX and DX had different fuel maps, redlines, etc. If the ECU is still controlling the engine as though it’s a stock CX, you aren’t going to get much power. You should also change the crank pulley - the b8 runs at 12deg btdc, while the b7 runs at 16. You can keep using your pulley, but you’ll need to add a few more timing marks to it, and it won’t be totally accurate. Best to just swap 'em if you can hunt up a DX pulley.

And unless yours is a California-spec CX, you’ll need to use a DX oxygen sensor and matching wiring.

There are a million and one Honda forums with guys that do these swaps hanging out there. You really should search round a Honda forum for the info you need…guaranteed they will be able to steer you to a solution. Im a bit of a good resource for the H22 swap into the Accord …removing the F22 stock Accord engine…but never dabbled much with the Civic swaps…


It could be both the injectors and the exhaust manifold…or, as already suggested, the ECU protocols or the cat converter.

I agree with Honda. Honda specific forum would be far more likely to yield a good answre for you. There are also Honda specific “tuner” magazines on the racks that are specific to Honda Civic tuning.

hey fellas, thanks for the reply. I considered the issue with the ecus’ being different, and i agree they do have differing fuel maps, however, I feel that should only have an effect of the higher rpms not just ‘basic acceleration’ a low speeds. There are no real issues with the engine and the only issue Im having is acceleration. Ive been reading a bit about throttle position sensor, and I feel this pretty much hits the nail on the head. The question I pose is if I buy a dx ECU do you think it would fix my issue? Oh and the honda forums are really limiting if you are new to their forum… I.e. they make you wait a certain amount of time before they let you post things in certain areas… its kind of stressful really…

Here. Go to mine: . Hit up Sikocivic with any questions you have - he’s done a ton of swaps and knows his way around D-series motors in his sleep.

Note that we’re about to go on our annual trip to the Vintage races - leaving early tomorrow morning, so you probably won’t get a reply until Monday.

No worries, thanks for linking me to your forum. That’s absolutely awesome. Thanks a heap!