[ffindling]

Chris - You probably won't have to deal
with EGR on replica car. Most people manage to register their cars in an emisions exempt category. EGR first appeared around 1973 as an attemp to
lower NO2 emissions. Since most OEM
intake manifolds have a heat riser passage that has exhaust gas passing
through it anyway, it was a simple matter
to install a vacuum-operated plunger valve that seated on the heat riser passage and when it opened it would
allow exhaust gas into the intake
section of the manifold where it would mix
with the air on its way to the cylinders.
The idea was that the spent exhaust gas
being recirculated would quench
combustion chamber temparatures to the
point where NO2 emissions would be reduced. In pre-ECM cars, the EGR valve
was usually operated by a coolant temp actuated valve. When the coolant reached a certain temparature, the
EGR valve would open. While EGR
may have reduced N02 emissions, it
also made the engine run lousy as one
might expect when you contaminate the intake charge with exhaust gas.
Back in those days, EGR was the first
thing that went when we de-smogged cars. You couldn't
simply take the valve off as that would
leave a hole between the heat riser
passage and the intake side. Easiest
fix was to simply swap intake manifolds
for an earlier non-EGR OEM manifold or
use a non-EGR aftermarket manifold.
If a non-EGR manifold wasn't available,
we'd either weld the hole shut or tap
it and screw in a steel plug. Then fab
a metal plate to cover over the hole
where the EGR valve was mounted.
Often just getting rid of the EGR made
the engine run much better with improved fuel economy. Since FE engines were phased out of passenger
car use in 1969, EGR is a moot issue
with them. Many aftermarket heads
don't have heat riser passages in them,
so EGR wouldn't work with them anyway.

....Fred