Work has had me busy and the engine project is in limbo anyway.
I ordered a David Vizard book on head porting. Really interesting stuff. I ordered a Taida big valve head. I plan to post some comparison pictures at some point. Anyone interested in discussing high-level GY6 head theory? Specifically, Vizard talks a lot about valve shrouding. I haven't pulled a caliper out and done any measurements but the head design looks like shrouding isn't really an issue.
There are a couple things I've read that are really interesting. This is still blowing my mind -
-On an engine with a properly tuned exhaust and intake, at TDC of the exhaust stroke, the intake experiences vacuum from the inertia of the exhaust exiting the exhaust port. This happens during the overlap period of the cams. The vacuum experienced at the intake can exceed the vacuum caused by the piston itself in its downward stroke. In order for this to happen the intake/exhaust have to be tuned, and there has to be good flow characteristics on the intake/exhaust valves at low lift.
Interestingly the book covers home flow testing with a vacuum. Basically everything I did was exactly what his book says to do except I didn't spend any time testing at low lift.
Currently I'm trying to find information on the Taida cams but I can't find anything. It is frustrating how little information is out there. I'm tempted to make a cam profiler.
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