Heavy Breathing (No, not that)

[Shannen Durphey]

Sounds to me (too) like ring blowby.  The reason the racers duct these vapors into
the exhaust (at least the ones who aren't copying everyone else) is that oil in the
fuel/air can cause detonation. And we all know what that means...  Also, if you are
considering this method, make sure you have some type of baffles in the valve
covers, and I would plumb one line from each valve cover to the closest header, (I
assume you are running them), and a third port, maybe the oil fill cap, should allow
filtered air in.  You can create quite a vacuum in the crankcase with this setup.

Just a note.  I know that a 300ci Ford 6cyl, though it has 8.5:1 compression,
produces higher psi readings during compression test than 350hp 350ci Chev V8 with
11:1.  Think it depends on valve timing and piston stroke.


dzorde wrote:

> OK, lets see:
>
> >Coupla questions:
> >
> >How much oil are we talking here?  Are you dumping quarts out the valve covers?
>
> No, its not that bad.  I would guess similar amount as to when you are
> refilling and miss the filler hole for that split second.  It just means
> that I have to regularly wipe the covers around the breather caps.
>
> >What kind of racing?  Straight ahead or left hand turns only?
>
> Real racing, left and right turns, on and off the accelerator, hard on and
> off the brakes.
>
> >What kind of vehicle?
>
> ehh, its a HQ Monaro.  I would guess similar to a 1973 Camaro in size and
> weight, except its a 4 door.

Umm yeah..  With this, I am out of my territory.  Know of any web sites where there
are pictures?  I'm curious.

> >What kind of compression?
>
> Not sure, I did a compression test and it came out between 225-240PSI on the
> cylinders, I think someone worked that out to be around 12.5:1 from just
> basic specs.  But I would think its quite high since it will only run well
> on 100 octane fuel.
>
> >solid lifters or hydraulic?
>
> Hydraulic.
>
> >quick reply is that you're getting blowby past your rings
> >some circle track racers plug the LH valve cover vent hole, and duct the RH
> vent
> >to a homemade venturi in the exhaust.  I've seen a coulpe of drag racers duct
> >both valve covers to the exhaust.
>
> Dan     dzorde at geocities.com