truckerlary

I have a Oldsmobile cast iron 4 barrel intake and on the plenium floor there are 2 holes about 3/8 in diameter. These holes are directly below the primaries. Are these holes supposed to be there and what is the purpose. I've just never saw this before as I've been pretty much a chevy guy. Thinking about putting this manifold on my 350 and want to make sure this is correct before i go to all the trouble. Thanks Larry

RandyS

Nooooooo, not good. There should be no holes there. That would allow raw gas to go right in to your motor and dilute the oil, ruining just about all the internals.

70vert

Is it an egr intake? If it is that's why there are holes there.

oldcutlass

x2

11971four4two

those EGR holes in the floor of the intake
can be drilled
tapped
and pipe plugged

but there are many
factory cast iron intakes without the holes
and many more aftermarket replacements too

happy motoring

truckerlary

It is a egr manifold. Will it hurt to run with these holes unplugged?

11971four4two

if you block the egr hole on top of the manifold with a sturdy
block off plate
you should be fine

joe_padavano

^^^This. The intake casting actually has a double-deck passageway under the carb. The lower passageway is the normal exhaust crossover for heating the carb. There is a port from this lower passageway to the EGR valve pad. The upper passageway is the EGR injection manifold that has the two holes. It is routed to the other port on the EGR mounting pad. The EGR valve normally closes this upper passage off from the crossover when the valve is closed. The valve opens during part-throttle cruise to enable EGR. As noted, if the EGR valve is removed and a block-off plate installed, there is no issue (other than the less-than-optimum flow disruption from the holes).