Re: [OMC-Boats] Pcv breather

From: jd <jdood@...>
Date: Fri, 11 Sep 2009 23:09:38 -0700

On Sep 11, 2009, at 2:57 PM, Lee Shuster wrote:

> Typically on boats of this vintage there is no Positive Crankcase
> Ventilation in the now-common automotive "PCV" valve sense.
> The standard OMC procedure was to connect a valve cover breather
> (rubber) hose between each valve cover on a V-block engine and the
> outside of the flame arrestor.
> The theory being as the engine throttle was opened the crankcase is
> ventilated by the pull of the low pressure into the carb. And re-
> cycling these back thru the carb, allows the engine to burn off
> these elements. One probably can't measure it, but in theory, at
> least, this helps increase fuel economy.
> Proper crankcase ventilation is important to allow "blow-by" fumes
> and gases somewhere to go. PCV valves were introduced on cars in the
> mid 1960's (earlier in California). Autos with PCV's differ
> (compared to our boats) by having a one-way check valve and instead
> of being routed into the carb inlet the are usually routed directly
> into a intake manifold "vacuum" port.
> Prior to PCV's you would typically see a meshed valve cover breather
> cap and have a road draft tube, but remember cars have free air
> access, not an enclosed engine compartment.
> Here's the "big deal" if you don't RE-connect you hoses: You engine
> compartment will gradually get filled with these blow-by gases which
> are potentially explosive, and depending on how "tight" you engine
> is a messy, oil film will appear on everything. It's also not so
> good for the environment (and your health) as the blow-by gases
> contain small amounts of unburned hydrocarbons. Chrome breather caps
> look cool, but will merely vent inside the engine compartment.
> Resist the temptation to use them and get your rubber hoses hooked
> back up. I know, you'll say you don't know where to find them, but
> they are out there.

no, actually i have a couple chrome ones on ea cover now that have the
tubes off the side which i route via a tee back to the SA. one
keeps coming undone and i wanted to temporarily cap it - that's what i
was wondering about.
> I've actually installed an auto style PCV on my small block Chevy.
> It did require re-adjusting my idle jets slightly.
> I've installed a clear catch can/filter so I can monitor or trap the
> heavy stuff.
> Lee
> -----Original Message-----
> From: omc-boats-bounces@... [mailto:omc-boats-bounces@...
> ] On Behalf Of jd
> Sent: Friday, September 11, 2009 2:55 PM
> To: Evinrude and 70's & Johnson Boats of the 1960's
> Subject: [OMC-Boats] Pcv breather
> What is the PCV valve breather for and is it a big deal if it's not
> connected?
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Received on Saturday, 12 September 2009

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