At 10:54 AM 12/27/2006, you wrote:
>Definitely don't plug the engine breathers. For best performance
>you'd like to run the crankcase at some amount of vacuum, to improve
>ring sealing, but barring that you want to make sure that the
>crankcase is adequately ventilated. You could run the right side
>breather into the header collector - that would burn off any fuel
>and oil vapors that come up through the breather, and the scavenging
>effect would ensure a constant flow of air through the crankcase.
The addition of air from any source to the exhaust system is a
complex situation. OEM air pumps make this "injection" very close to
the exhaust valve. Injecting air farther down the exhaust system
generally leads to the same cracking and snapping you get with a
leaky exhaust system. It becomes very apparent when you go into
close throttle mode.
I attempted to build a negative pressure crankcase system in the
early 70's (great theoretical concept), dumped the discharge half way
into the cast iron exhaust manifold, and ran headlong into a Tiger
that snapped and popped every time I backed off the throttle. I
lived with that for maybe a month and decided that wasn't the way to
reduce crankcase pressure, and pulled all the hardware. Never did
spend the time to develop a functional design. The properly
installed PCV system is hard to beat.
Tom Hall
ModTiger Engineering LLC
www.tigerengineering.net
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