Message text written by INTERNET:Ct54531@aol.com
>What is the proper original setup with regard to the PCV valve -- or
>regulator (EGR, maybe?)
>On page 92 of my Haynes manual, it shows what is described as the
"Crankcase
>Breather Regulator Valve Details", with a hose from the valve cover to -
PCV?
>regulator? EGR? -- and from that to the intake manifold.
>What my car has had is a piece of hose about 3 feet long running from the
>valve cover to..um...nowhere.<
Jim, the TR4A has a crankcase regulator valve (which is often refered to as
a
PCV or Positive Crankcase Ventilation valve which modulates an opening to
the intake manifold to maintain a slight negative pressure on the
crankcase.
The benefits of this system is to purge blowby gasses from the crankcase
which
would otherwise foul the oil and to reduce the tendency to leak oil while
running.
This system prolongs the life of the oil and allowed the manufactuers to
change
their recommended oil change intervals from 3,000 miles to 5,000 miles
(5,000 KM
to 8,000 KM). This device was not added to meet US emissions standards and
it
actually predates the commencement of the emissions regulations byt several
years.
The valves used on british cars used a rubber diaghram that tends to perish
over
the years and when that happens the valve can cause a couple of undesirable
effects
such as excessive oil consumption. When this happens some owners used the
expedient of removing the valve and ducting the discharge from the
crankcase to a
low point (via a hose) where the atomized oil droplets will not soil the
engine bay. I
suspect your hose terminates somewhere near the bottom of the engine. Some
put
the end of the hose in a catch tank to catch the small amounts of oil that
will accumulate.
>So what's the proper setup originally. I looked in Piggot but the only 4A
>engine photo I saw had the round air cleaners (I have the oval ones) --
and a
>setup where the tube ran from the valve cover straight ahead to a
connection
>that then split. On my car, on the manifold, just behind the rearward
>carburetor (Stromberg), is a projection which has been quite thoroughly
>plugged. I have a parts TR4 sitting next to the 4A in the garage and it
has
>no similar orifice on its manifold. Am I correct in assuming that's where
the
>hose from the regulator to the manifold would go. And why was it removed?
Is
>there a performance issue? What's the effect of the modifications and is
it
>worthwhile to put it back to original?
The pictures on page 62 on Bill Piggott's book show another method of
purging the
the crankcase but this method provides a purge that varies with throttle
and engine
speed. If you turn to page 67 you will see a picture showing the valve and
it's
connections which are probably what your car had originally.
Graham Robson's book "Triumph TR's" has a pretty good picture on page 43
that shows the valve and the two connections - one to the rocker cover and
one to the manifold behind the rear carb - from another angle. I would put
it back
to original or failing that do what some have done and substitute a modern
PCV
valve in it's place. There is no performance advantage to either way but
the oil
will stay clean longer with the system intact.
The TR6 (and other late TR's) used a special connection on the carburettor
that
ports to the venturi and since these are Constant Depression (CD)
carburettors
the slight vacuum at the venturi (which is constant) provides the purge
action without
the troublesome valve. But you must have the carbs with special port.
An EGR (Exhaust Gas Recirculation) valve is a device to reduce NOx
emissions
and was never fitted on a TR4A (except for possibly research purposes).
Dave Massey
St. Louis, MO USA
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