Re: Why did all of my exhaust valves look like this?

Posted by humanpotatohybrid On 2024/5/29 11:34:09

Either soot build up from the exhaust, or excess oil leaking in, carbonizing onto the hot valve.

Intakes aren't as bad because only clean air flows by them and they don't get as hot either. Though because there is a vacuum in the intake manifold, compared to positive pressure in the exhaust, it's easier for oil to get sucked in on the intake side. So at least on the V8's, which are OHV, the intake side were equipped with little rubber boots.

Party trick: wet your finger and then you can hold it in the flame of a lighter without burning yourself. Though your finger will become dark with soot after just a few seconds. So it's amazing the engine can stay as clean as it does.