Brian, you are correct, the vent tube draws fumes and of course pressure out
by the vacuum created by the air moving past it as you drive down the road.
However Bill's comment is not entirely accurate. The design of the interior
of the block as well as the tube itself limits the amount of oil that can
actually be drawn out. What does escape is really very minor.
The 4A system does not use a vented cap or the draft tube.
>
> Don't you have a vented oil filler cap on your TR4? If there is excessive
> crankcase pressure, this should handle it easily without have to add the
> vent from the TR3, which can be another source of oil leaks unto itself.
> Regards,
> Bill Beecher
>
> My TR4 has both the breather cap and the block vent. I thought that while
> the cap allows pressure to escape from the head, the position of the vent
> tube 'out in the wind' was to draw gases from the crankcase through some
> sort of pressure drop at the end of the tube as the car moves. I may be
> wrong.
>
> Brian
>
> _______________________________________________
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