I got a b16a in my 2000 civic si. not original motor first one blew, second one worked for almost 2 years, then one morning we started up and wont start. we checked mostly everything, the main problem that we found was that it had low compression in a few cylinders, and did a leak test with a air compressor and air was coming out of the exhaust and intake manifolds (we removed the headers and intake manifold). we removed the head and the pistons looked fine, the head is too, the oil and antfreeze hadnt mixed so couldnt be a cracked wall. Here are a few of my guess, microfractures on he side of the pistons wherethe rings are, bad valves, bad valve stem seals, bad head gasket. but heres the thing i didnt get, we poured water into the cylinders and water isnt going down the pistons, we did the same for by pouring into intake and exhaust of the head and still no leaks, its pretty weird, any ideas before i just start pouring money into it, lol.

 

cam timing was prob off? I wouldn't ever pour water in your cylinders, its just asking for rust.

 

well dont think its cam timing, because its not constant through out all cylinders, and air did leak through the instake and exhaust side of the head. the pistons did have alot of black buildup on them probably because it was buring oil,

 

It turns out something might of gotten into the combustion champer. The top of the combustion chamber of the head was pretty beaten up. we switch out with a new head and now works fine.