D15B vtec, D15B(w/3-stage)vtec, or B16B type r vtec
 

im looking to put a vtec engine in my 1996 honda civic dx. i do not kno the difference between the 3 different engines and need help figuring out which one will fit and has more power. please help!!!!!!!!!!!!

the 3 stage vtec is known as vtec-e. basicly it shuts 1 intake valve per cylinder off at low rpms and at low throttle to basicly create a swirl effect on the atomized fuel for more efficient combustion. then ( i believe) at 2500 rpm to 5000 or so it kicks the extra valve on for an extra bit of hp output. and finally at very high rpms, 5000+ or under w.o.t. it switches both intake valves over to a higher output cam lobe for extra performance. while all this sounds great, if your just looking for performance, a b series with just the dual stage vtec is much better. the dual stage uses all 4 valves per cylinder at all times, it just switches between a mild cam lobe and a wild cam lobe.
the difference in the amount of "pull" between a sohc vtec and a dohc vtec is much harder in a dohc. because of the spark plug placement in a sohc, they can only switch the intake side over to the wild cam. with a dohc vtec they switch both the intake and exhaust side over from mild to wild. a dohc engine will also tend to rev to much higher rpms.
just google how vtec works and check it out. its pretty simple, its basicly just an oil driven pin that connects the rocker arms together. this was about as simple as i could put it while still trying to educate you on the difference but to get the full effect, either google and look at some pictures of a vtec sohc, a vtec dohc and non vtec sohc and dohc heads without the valve covers on. count the rocker arms.
once your done with that, look up i-vtec. its the best system honda's made so far, featured on the civic Si's from 01+ and the rsx type s.
hope this helped a little bit!

the type r, usdm, is a b18. same dohc vtec design, just more displacement

the h series (preludes) have dohc vtec systems as well.

and instead of creating a new thread, try the search bar. most likely someone else has had the same question