flapper in air intake hose

[gmbellew]

what is this? the hole on the bottom is not connected to anything. stock 1990 350 tbi in a v1500 suburban.

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[Customblue]

Heat riser pipe? From the exhaust shield I believe

 

[gmbellew]

yes, it looks like it just took radiant heat off the shield. any issues with it not being connected? should I plug the hole on the intake to keep engine air out of the exhaust? or should I connect it back?

the little pintle seems to be well stuck and frozen in place at this time. so I assume the flapper just sits in there horizontal all the time.

 

[skysurfer]

Check it with a hair dryer on the hottest setting. Aim the dryer at the gold knob and see if the plate rotates. If it operates correctly, get some flexible heat riser tube and hook it up (assuming your exhaust manifold adapter is still there).

 

[gmbellew]

I have been looking at the manuals. this thing exists to warm the engine up quicker when it is cold outside by feeding radiantly heated air (from the manifold shield) into the engine. there is a calibrated spring that would normally keep the flap closed to cold air until the thematic switch (expanding wax) pushes the rod out to force the flap open to cold air as the engine warms, closing off the heat riser pipe. the spring is long gone and my flapper just stays open to cold air all the time and closed to the old heat riser (now just engine compartment air).

I wonder if the flap ever bounces around when driving. I have never noticed an issue in the couple years I've had the truck. when the weather gets better I may either remove the flapper and plug the hole (theoretically improving airflow because no flapper) or just make sure the flapper stays open and the bottom hole plugged all the time.

the more you know!

 

[Octane]

It'll take in more air leaving that baffle open.Wont hurt anything.