[TR] TR4 engine rebuild/rear seal

[Randall]

> It occurs to me that venting fumes to the atmosphere is 
> contrary to the
> spirit if not the letter of the emmissions rules for these old cars.

If that bothers you, you could add a PCV valve to suck fumes from the rocker
cover when there is manifold vacuum (which is most of the time); and bring
the large vent hole in the side of the block out and up to an air filter
with large diameter tubing.  That will give you a proper Positive Crankcase
Ventilation system (which IMO Triumph never did get right).  This is the
configuration used by virtually all American cars.

Under cruise conditions, the fumes are sucked through the valve into the
intake manifold and burned, while the filter admits fresh air into the
crankcase.  Then at WOT (where blowby is maximum but no manifold vacuum and
hence no flow through the PCV valve), the fumes go out the other way,
backwards through the filter into the atmosphere.  But the large diameter
tubing (and hopefully free-flowing filter) prevent pressure buildup in the
crankcase (which I agree is one of the major reasons these engines leak oil,
both at the rear seal and at the rocker cover gasket).  

All this is theory though, I haven't tried it myself yet.  But after reading
up a bit on how much gunk goes into the air from the road draft tube; I will
be adding this to my project TR3.  It should also help the engine last a
little longer, by reducing varnish buildup from condensing blowby, and by
reducing dirt sprayed into the road draft tube by occasional off-road
excursions (both intentional and unintentional).

Likely you will need to disconnect and plug the PCV valve while setting
mixture.

Randall