Dave Binkley wrote:
Steve,
I was reading through the CAT shop notes last night and found reference
to a question about what to do with the PCV hose if you're putting a
Holley/Edelbrock combination on and you don't have an appropriate
spacer. The reply was to just run the hose to the air cleaner.
How does your infinite wisdom react to that suggestion?
Thanks for all the help,
Dave
B9471930
Plainly,
It "sucks". The PCV control valve is controlled by manifold pressure (vacuum),
and regulates the amount of crankcase fumes that are
recycled through your combustion chamber. This burns the residual blow-by,
oxidizes the gases that got by the rings, and the hot fumes
from whatever is in your crankcase. This oxidation reduces the pollutants,
without significantly affecting your performance. Helps more
than it hurts.
The air that replaces the fumes comes from that rubber hose from the inside of
your air cleaner (clean air) and goes to your oil fill cap. There
are passages in the head and block that allow this air to purge the crankcase
blow-by, and reduce crankcase pressure (which works
against your pistons, because it's on the wrong side). The original Tiger PCV
valve was able to be taken apart by a simple circlip tool,
cleaned, and reassembled with new spring or valve, if required. Someone had
assembled mine backwards, and I corrected it before
reinstallation. The valve is most open at high manifold vacuum, and just has a
small bypass at low vacuum. So you are purging the most
at idle, and more importantly when your backing-off or coming down a grade with
your foot eased back. So, when your really "on it", the
valve is practically (but not fully) closed anyway.
If you plumb it to the air cleaner, your connecting the "goes-into" to the
"goes-out-of". This is rarely known to benefit anybody, and is most
uncomfortable for the engine. You don't believe me? Try it by connecting your
own "goes-into" and "goes-out-of", and tell me if it "feels" better.
{8->
Steve
BTW: The '69 Boss Mustang had a 1/4" spacer with a 9/16 " PCV Tube. They
squeeze the metal tube into an oval where it mates the plastic
spacer. Still available from your friendly dealer for $34. If they have a
"Mustang" club discount I got 25% off. Of course I had a Mustang,
and was a member, but they didn't need no "Steekin' Badges". Depending on your
carb and air cleaner, this might work. On an F4B, with
a slightly fatter gasket (better than paper), an 1848-1 465 CFM Holley, and a
stock air cleaner there is clearance over the nut (NOT WING
NUT) on the air cleaner with this spacer. Did have some paint rubbing contact
with the front edge of the air cleaner and the downslope of
the stock hood. Depends upon how new your motor mounts are, and mine were new.
The newer 1850, although 600 CFM, rather than
465, has a built-in tube. I swapped bases and got what I consider a better
town/road carb and the PCV port, without the spacer, or the
rubbing. Aye, there's the rub. --- I'd continue, but enough is enough.
--
Steve Laifman < One first kiss, >
B9472289 < one first love, and >
< one first win, is all >
< you get in this life. >
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