Message text written by "Jim Davis"
>I run CF38690 with the bypass valves blocked. It was recommended by a
racer several years ago at Road Savannah. It works great for me and no
damage that I'm aware of. The only downside is that there is some
popping when decelerating (from the richer mixture as no air is being
sucked in).
<
I remember reading (somewhere, probably in the Haynes manual) that when the
vacuum reaches a certain level the mixture will no longer combust and you
get unburned hydrocarbons in the exhaust. On cars with catalysts this
mixture will ignite in the converter (which is very hot). On cars without
converters this mixture may ignite if the exhaust manifold has any hot
spots hot enough to initiate combustion, otherwise the hydrocarbons will
exhaust to atmosphere. Since this is a transient situation there is little
contribution to the overall air quality considering the small number of
LBC's on the road and the amount they are driven.
The bypass (over-run) valve is designed to keep the manifold vacuum below
this point and eliminate these issues. But when they get to be 30 years
old the diaghrams tend to get stiff and will split and the resulting leak
causes other problems and if diaghrams are not available, blocking these
valves off is a better solution than driving with a faulty bypass valve.
Besides, blocking them off is a handy diagnostic tool in determining if
they are indeed the cause of the problem. I think in this particular case,
Hugh found a torn piston diaghram was the problem and blocking off the
bypass valve would have resulted in no change pointing him elsewhere for a
solution.
Cheers
Dave
/// triumphs@autox.team.net mailing list
/// To unsubscribe send a plain text message to majordomo@autox.team.net
/// with nothing in it but
///
/// unsubscribe triumphs
///
/// or try http://www.team.net/cgi-bin/majorcool
|