The butterfly in the exhaust manifold is a heat riser. There should be a
bi-metal spring attatched to it that will hold it closed when it is cold and
allow it to open when hot. The purpose of this is to improve cold
driveability by closing off one side of the exhaust and send heated exhaust
through the passage in the intake manifold and out the other exhaust pipe
until the engine reaches operating temp. The warm air helps eliminate cold
driveability problems. If you can not find a replacement or are not worried
about a little stumble when cold, wire it open so it does not rattle and
forget about it. Make SURE that it is open. I have seen some cars where it
was installed backwards. The heat riser is supposed to open by also by
exhaust pressure(when you rev the engine) even if the engine is cold.If it
is in backwards the exhaust will push it closed,create a restriction in the
exhaust,causing not only loss of power,but generate ALOT of heat. This is
not good for the valves,which will accumulate deposits rapidly. The worst
part is, if you look at how close that heat riser is to the floor pan and
the passengers feet,you will know why it has to be open. I have seen a few
floorpans melt because of this. They were installed on all the cars. As for
the gasket, try a muffler shop. The gaskets are usually a composite of high
temp material and/or metal. Do not use standard gasket material.
RE/ fuel pump block off plates. Achevy one should work. Back in those days
there were only two shapes of fuel pump bases. The one like the
Chevy,Dodge,Ford(triangular) and Olds that was thin with the bolt holes on
the top and bottom instead of on the side. We used to leave the mechanical
pump on and use it as a pressure regulator rather than eliminate it. If you
use an adjustable pump, Just make sure the pressure is not too high or it
will rupture the diaphragm in the mechanical one. I would install a pressure
switch,or tap into the existing o.p. switch. The purpose of this is in case
of rollover or stall , when the engine quits the fuel pump does not keep
pumping. God knows these car are prone to fire anyhow,why add to it?
-----Original Message-----
From: Olenick, Jamison <Olenick@ssims.nci.nih.gov>
To: 'Bricklin' <Bricklin@autox.team.net>
Date: Wednesday, August 12, 1998 8:26 AM
Subject: Butterflies in Exhaust
> Can anyone tell me why there are butterflies in the exhaust at the end
of the
>manifold. There are weights on the pivot point that hold the butterfly
closed
>and there seem to be some sort of spring to help it open or close...but of
>course the springs are broken/deteriorated and useless...which makes the
weight
>hold the butterfly closed.
> Does everyone have these or were they on just a select few? (#23 to be
>specific)
> Has anyone removed these?
> Do they actually serve any purpose other than to restrict air flow and
hurt
>performance?
> Also.. anyone found the gasket that goes on this exhaust joint? My
local pep
>boys did not seem to be able to get me one. They suggested buying gasket
>material and cutting one out myself. I did this but I think that it is
going to
>get burnt up due to the tremendous heat there.
> Any suggestions?
> Third..I just bought an electric fuel pump for the car. Anyone found a
plate
>to cover the old mechanical fuel pump hole on the engine block or is that
>something that just has to be improvised? (Summit or Jegs sells the covers
for
>Chevys and Fords) Wiring - should the pump be wired to an oill pressure
switch
>or is it OK to wire the pump so that it comes on with the ignition switch
before
>the motor actually starts.
> Thanks
>
> Jamie
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