So I have recently swapped my 97 civic with a b20b high comp. I finally got it to turn over today with lots of hours and head scratching. WELL It starts but it immediately revs up to 4k and sits there and idles at 3-4k. I haev my iacv and map sensor plugs in the correct place since it runs just fine, and to my knowledge there are no vacuum leaks. Just as something to take into consideration, this is an LX and I removed the cc device and the cable for it as well as pulling the small canister for it and removed the vacuum lines, I dont think its connected to the main vacuum lines but it is just food for thought. I am very confused and would love any sort of help!

 

An engine can't run that fast without air. Something is lettling a lot of excess air into the engine. Throttle cable too tight, vacuum hose disconnected (especially check the brake booster) mismatched intake parts or gaskets that leave an air gap.