On Tue, 1 Jun 1999 22:14:46 -0700 (PDT) walker05@camosun.bc.ca wrote:
>
> On Tue, 1 Jun 1999, Jerry Oliver wrote:
>
> > Does anyone have an idea what effect not having the breather plug in the
> > block on a closed system engine would have? I was under my car (66 TR4A
>
> Oil vapors escape and cause quite a large oil spot somewhere in your
> engine bay.
>
> On my TR4, which has a TR4A engine and no PCV (just a stub sticking out of
> the valve cover- I intend to do something about it someday...), there's a
> football-sized "spot" on the underside of the bonnet. I notice no
> problems with the engine. (However, I've never been priveledged enough to
> witness what a TR engine is supposed to be like)
>
> If you have a hole in the side of your block and no draught tube, either
> install a plug or a draught tube. The tube has a 'trap' in it to stop
> anything nasty (water and brake fluid come to mind) from getting into your
> engine. I vote for the plug, especially if you have a breather on the
> valve cover.
>
>
Malcolm,
I usually agree with you... but not this time. I also have 66 TR4A engine in
my 62 TR4. I was not happy with look or more importantly the terrible design
and function of the PCV valve setup. It had bad variable air leaks which
caused highly variable idle and mixture.
I beleive that it important to do one thing or the other. If the hole is open
you must have a valve cover that has the breathing oil filler cap and you must
have the draught tube installed. The venturi shape and angle of the tube
provides a pro-active air flow through the engine and negative pressure to
clean out exhaust gases and what not.
In the PCV setup the engine is sealed up tight and the blowby gases are sucked
back into the intake stream and the PCV valve is supposed to maintain this
negative pressure inside the engine.
The negative pressure is important to the rear seal operation. Without the
negative pressure provided by one setup or another.... the pressure pulses
inside the engine will blow oil out past the rear seal which depends on air
flow into the engine.
I experienced this when I first bought my car. The PO had put a cork in the
PCV hose to stop the air leak and had not changed the valve cover arrangement
and the car pumped oil out of the rear seal. I removed the cork and the ALL
oil leaks stopped but the engine was a very unstable at idle and setting the
mixture was imposible.
I have retro-ed my engine back to the full breather setup for both originality
and the better engine behavior. The engine has a rock steady idle and better
control and I can start tuning the mixture more precisely.
I have an extra draught tube and early TR4 valve cover from a junk yard engine
if it will help you or Jerry.
Brian Sanborn
62 TR4 CT16260L - Groton, MA
sanborn@net1plus.com
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