> On the '70 model year, for evaporative control reasons, the vents on
> the fuel float bowls were routed into the air cleaner instead of venting
> to atmosphere. A side benefit is that only filtered air is supplied to
> the bowls.
I had read on one of the websites that at high rpm driving there was enough
vacuum at high rpms to create a vaccum in the fuel bowls and starving the
carbs. I did notice that the engine would top out at about 5000 rpm with
the overflow connected to the air filter housing, rerouting to atmosphere
allowed the engine to rev past 6000. But aren't the purpose of the tubes is
to direct fuel overflow into the carb in case of blockage? I don't think
that the air is supposed to be drawn into those tubes back to the carb.
>
> The attach points on the air cleaner are neutral pressure - that is, they
> provide no vacuum draw (assuming a clean air filter :-) ). IMHO, this
> routing has no detrimental effect on performance, and possibly a
> negligible improvement for the air we all breathe.
Are you refering to the 1/2" PCV Tee connection at the aircleaner?
> The PCV fitting in the middle is different. Assuming there's still
> the rubber 'tee' inside the housing, this fitting does run at a vacuum.
> There are venturi tubes in each internal airhorn, and the air flow
> thru the carbs creates a slight draw to help keep the crankcase
> ventilated.
Aren't these the 1/4" tubes that go to the carb and not the PCV?
Steve
----- Original Message -----
From: "John F Sandhoff" <sandhoff@csus.edu>
To: "Stephen Wan" <Steve@olsonarchitect.com>
Cc: <datsun-roadsters@autox.team.net>
Sent: Thursday, March 25, 2004 11:13 AM
Subject: Re: "PVC" on valve cover...
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