Help identifiying this thing

[daveccpa]

I am trying to help a buddy out with his truck. What is this port/opening in the passenger side exhaust manifold? Can it be plugged or should it just be replaced. The engine is a 1995 SBC350 v8 from a chevy Tahoe.

[mongocanfly]

Does that hole go into the manifold or is it just a shroud around the manifold? There used to be heated air going into the breather from a shroud around manifold years ago
This is what's shown for a tahoe..and that's a heat shroud..

[daveccpa]

The hole goes into the manifold. I wondered if it was some kind of pre-heater or something

[dsraven]

it is a heat stove shroud that should have a section of vent tube going to the air filter housing. the housing has a vac operated door that opens to allow heated air to enter the air filter housing in the snorkel bfore the round part of the housing. the vac is run through a temp sensor in the main part of the housing which opens or closes the heat stove door. this is to prevent icing in the throttle body on cold days when there is possibly more chance of freeze up from ice build up through the venturi effect in the throttle plate area. I have seen guys stuck on the side of the road due to no warm up period for the engine and also deleting that stove, or the guy at the oil change place didn't connect the stove properly when he had the air filter housing apart for a filter change. maybe not a big deal in warm climates but for sure required in areas where it snows. the throttle plates can be encased in ice, i have seen it. below is a pic of a truck I found on google and it shows the end of the heat stove tubing connected to the air filter snorkel. it is flexible and heat resistant vent tube. below that is a hotrod netwrok write up and if you scroll down you will also see the tube in question

http://bobby.ledbettercars.com/cgi-bin/md/M11792/s12.pl

http://www.superchevy.com/how-to/148...power-upgrade/

[dsraven]

update
sorry, can't totally remember if there is vac run to that heat stove door on the snorkel. been awhile since I looked at one. thinking yes but not totally sure.
anybody else?

[dsraven]

also, the hole doesn't actually go INTO the exhaust portion of the manifold, it should just be a sheet metal shroud around the manifold that collects heat. if it has carbon in the shroud then look for a cracked manifold. very common in those years. if the engine is running, cold especially, you will usually hear a pfft pfft of exhaust leak in the area which can be quickly found where from with a bare hose stethoscope. (a length of hose with one end in/on your ear and the other end probing the area for the noise).

[1project2many]

Originally Posted by dsraven

update
sorry, can't totally remember if there is vac run to that heat stove door on the snorkel. been awhile since I looked at one. thinking yes but not totally sure.
anybody else?

It depends on the engine and fuel system. Centerbolt valve covers are '86 and newer. During that time a car, or a carbureted truck would have vacuum to the "ThermAC" unit. A TBI truck would have no vacuum but a thermostatic valve would keep air temp above 90 degrees.

The engine in the picture seems to be a bit of a mismatch? It's got vacuum advance and the exhaust manifold heat stove is in the center like a pre-'82 vehicle.

[mr48chev]

They nailed it. that is for exhaust heat off the manifold to the air cleaner for cold day running until the engine warms up.

He can pop the rivets out and take it off if he doesn't run an air cleaner to match but what's under it may be just as ugly as it is.

[Coupeguy2001]

I still got a set of those collecting dust.
yep heat shroud