How much of an effect does an engine rebuild have on smog emissions? If you just hone, replace the rings and valve seals, then will the motor run as clean as if it's a brand new engine? Does doing things like replacing the oil pump, oil screener, bearings have any effect on smog?

 

Sounds like someone has a problem they are trying to fix?

As for your initial question (hone, replace, run like new?), no, not like brand new but better than old (don't forget the valves themselves could be bad). But CAN it help (depending on why you are having problems with emissions)? Yes. Can it hurt? Yes (if parts are past tolerances after hone etc.).

I guess what I am saying is it depends . It depends on why you are not passing emissions, it depends on how bad your cyclinders and rings are, it depends on whether or not you need a just a hone or a full bore (in which case you would need new pistons etc.). Are your comp numbers that bad?

In general, yes fixing your combustion chamber will help you with emissions (depending on what is wrong. And keeping in mind the break-in for rings). Are you high in HC's? Are you high in CO's? Are you running lean? Are you running rich? Are you burning lots of oil?

As for bearings, no effect. As for the oil components your mentioned, no. They are basically there for keeping your mechanical components from wearing out and burning up (of course, we all know about the PCV valve and oil etc.).

Maybe I'm reading more into this than you intended, lol. Maybe you're just in the middle of a rebuild and the question came to your mind. But its hard for me to answer that question without making disclaimers

MB