I got a 70,000 mile h22a all stock intenals. to start, the past few weeks my cyl#1 spark plug has been building up alot of carbon on it, like crazy amounts... the other day my car started running like crap. i pulled over and we pulled the spark plugs; they were black as hell! we brought it back to my friends garage and there was no compression in cylinder 1. we pulled open the motor thinking the piston rings were shot... pulled out the piston in cyl#1 and the rings (after i bought them, of course) and they looked fine... so we took a closer look at everything.. turns out the top of one of my intake valves (cyl#1) was missing a nice little piece out of it. im awaiting the machine shop to look at it. anyone else broke a valve before? any helpful input would be great. thanks.

 

It's caused by excess carbon build up.

Carbon gets on the valve. Valve can't transfer heat to the head. Overheats and cracks.

You can check for a sticking injector.. maybe the PCV system is messed up. How do the other cylinders look?

Valve seals leaking oil down the valves and depositing carbon will do the same thing.

Had a customer a while back bring in a 99 civic SI with an intake and his #3 valve was chipped. Machine shop cleaned up the ports, put in a new valve, recut the seat. Hasn't had a problem til today.

 

the other cylinders seem to look fine. ive been using quite a bit of oil and coolant as well and theres no leaks anywhere. head gasket and valve seals, do you think that might be the culprit?