[TR] Vented Crankcase

[Paul Dorsey]

If some later TR4A engines were closed ventilation (improving air quality at 
no expense to performance), why then were the earlier engines vented? 
Especially if venting them was detrimental?  I KNOW THAT THEY WERE NOT 
THINKING ABOUT THE ENVIRONMENT.
        Also, I think we're talking vented engines as being:
intake vent- at the valve cover
exhaust vent- being the road draft tube
Is this right?

Thanks,
Paul Dorsey