> Actually that occured along the way in the TR4 line (before TR4A). My
> '64 has no draft tube but I'm not so sure about the "PC" in the PCV.
The draft tube was lost mid-TR4, but I believe the PCV valve was a 4A-only
item.
> Seems to mostly ventilate the valve cover, not so sure there isn't
> pressure build up in the crankcase that would be relieved by having a
> breather on the side. Is this a normal state of affairs in the late 4's?
Yes. Each pushrod tube serves as a vent from the crankcase area back up to
the rocker cover, so there is plenty of vent area there. I suspect that
with a worn engine, internal pressures might be a little higher, because the
tube from the rocker cover to the air cleaners is smaller diameter than the
old road draft tube, but that is the original arrangement for late TR4. Not
a very satisfactory system IMO (and definitely not Positive Crankcase
Ventilation) ... since there was no fresh air intake to the crankcase, it's
always full of blow-by fumes when you shut the engine down. They contain
water and acid that tend to condense and contaminate the oil.
The 4A system was closer to a modern PCV system as it supposedly did have a
fresh air intake. Just guessing here, but I suspect it's intake was too
small, leading to high crankcase pressures after prolonged zero vacuum
operation. Any comments on this from those of you who flog TR4As ?
Randall
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