i have a newly built b20v engine that's just finished breaking in. I was looking at the exhaust ports when I noticed the exhaust valves on no.1 cylinder were clean of deposits on part of the stem. all the other exhaust valves look normal, as in they were all evenly covered with carbon.

any comments?

 

that guide might be tighter than the rest

 

Are the exhaust valves in cylinder one open?

Rotate the cam and see what the other stems look like in the open position for each cylinder.

I'm not 100% without seeing the other three sets of valves. However, I would say that is just normal stem open and close conditions. The carbon does not get the chance to build up on the portion of the valve that moves up and down inside the guides.

Those marks should be uniform on the other valves as well.

 

^^excellent point

 

you're probably right, thanks for the inputs