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Dale,
I should have
mentioned that the cowl is closed all the time and won't open when you punch it.
However, a buddy of mine mentioned to me last night that he thought the cowl
induction ran off ported vacuum not manifold vacuum. I haven't looked into it
far enough yet to sort it out but I suppose that is possible,
too.
It may become a
moot point as I just found an old Edelbrock cross ram manifold for a BBC that
mounts a pair of 4 barrels! It may not run worth a crap but it sure would LOOK
cool! I may even sacrifice an operating cowl induction to mount that puppy under
the hood.
Craig
Craig,
I assumed the cowl vent was open all
the time and not shut all the time; although the poster didn't specify
which. May be a bad assumption on my part (?) Being open
all the time would be an indication of no manifold vacuum at the valve to
close it under normal driving conditions or when at idle. I don't know the
vacuum hose routing from the flapper valve but the line may be pinched or the
valve is bad. Since you would normally have 14-18 inches of vacuum at
idle, that should be more than enough to close the flapper valve. I
would assume it opens at somewhere between 5 and 10 inches of vacuum when you
nail it.
Whether this has anything to do with the
carb secondaries I would doubt since they're operated at the carb via the
spring - unless the carb has recently been rebuilt and not put back together
properly but I think they're be a sucking sound you could definitely
hear. Unless you can feel when the secondaries open under a load at WOT,
I don't think you'll see them open just winging the engine while you're
watching it. And I sure hope you're not testing it like two guys I read
about that got stopped in a car with the hood off. One guy was sitting
in the engine compartment to verify the secondaries were opening while the
driver was hauling a$$ down the road!
Dale, that's
what I've always thought but I think the cowl induction system works
manifold vacuum drops - as in when the throttle is punched wide open. My
understanding is that vacuum is what keeps the cowl closed - that's why is
snaps open when you turn off the motor. I am not a mechanic and could be
wrong about all this - but the logic of the system seems to indicate this is
how it should work.
Craig
E
I wouldn't think so it'd be possible to
generate too much vacuum. Both my cars (396 and 327) pull about
17/18 at warm idle, 15/16 cruising at steady throttle and jumps to 24/25
range when decelerating.
You problems sound like lack of vacuum -
bleeding off somewhere.
Dale McIntosh
ACES #1709/TC #92
Gold
67 SS/67
Elky
http://www.dalesplace.com
http://www.team67.com
http://www.midwestchevelles.com
Is it possible to generate too
much manifold vacuum and, if so, how does one diagnose the problem and
remedy??? My cowl induction has stopped working and my vacuum
secondaries appear to be malfunctioning. I'm wondering if the problems
are related...
CAE
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