Removing THERMAC system?

[LukeZ]

anyona have any experience removing the thermac system from a stock engine? Mine is a 1986 305 specifically, and I'm just wondering. I want to get shorties and a new air cleaner assembly, but I remembered that I have all of this stuff to worry about before I do that.

In case you don't know what it is, because I'm not sure if all cars came with it or what, it's pretty much a system that draws hot air from around the exhaust manifold when you first start the car up. Air is cut off from everywhere except a tube that runs from the area surrounding you manifold to the air cleaner snorkel. After the engine warms up, the snorkel on the air cleaner opens up and runs on cooler air from the engine bay.

I'd assume that you would just have to take the casing off the exhaust manifold, remove that tube from the casing to the air cleaner, and take out all of those vacuum tubes that open the snorkel and all that. Does anyone know if that would cause problems with the engine, having all those tubes just disconnected? Thanks

 

[565bbchevy]

Usually you would remove all of that when you install headers since most put on a free flowing aftermarket air cleaner but if you wanted to retain the stock air cleaner assembly you could probably fabricate something using the two center header tubes but I don't know if work as well as the factory set up but it might.

 

[565bbchevy]

Here is a picture of someones attempt to use the factory air cleaner obviously it can be made differently.

 

[clean8485]

As I understand the operation of the thermac system, its there to help the engine warm up more quickly in cold temperatures. The flap in the air cleaner snorkel closes when the engine is cold, so it draws warmer air from the heat stove area around the exhaust manifold, then as the engine warms up, vacuum draws the flap open, so that the engine will draw in cooler air from outside the end of the snorkel.
Most people who eliminate the thermac system will remove the stock air cleaner assembly, plug any open vacuum lines/ports, remove the tube that carries the warm air from the exhaust manifold area, and install an open element air cleaner, or some kind of cold air induction system. Its not necessary to remove the heat stove from the exhaust manifold, unless you find it unsightly. I know in some cases, that heat stove also supports brackets that hold spark plug wire looms.
Keep in mind that in certain juresdictions, the thermac system is considered as part of the factory emission control system, and it may be considered illegal to tamper with it or remove it.
Hope this helps.

 

[Bonnewagon]

Keep in mind that the factory carb is calibrated to function correctly when it is fed 100 degree air from the THERMAC system. Anything you do to upset that relationship you will have to deal with the consequences. If missing, in July you will be fine but in February the car will run like total crap and take 30 minutes to reach operating temp, if at all..

 

[Chevhead78]

Isn't part of Thermac also the flapper valve on the exhaust of most vehicles to also help warm the engine up to operating temp sooner? I used to have alot of people come in trying to get the gasket for that piece and I remember really digging to find something that would work.

 

[pontiacgp]

an open air cleaner will make the carb run richer.....and I thought you started a thread a few months ago asking about how to heat up the engine quicker...

 

[LukeZ]

an open air cleaner will make the carb run richer.....and I thought you started a thread a few months ago asking about how to heat up the engine quicker...

I did but I like bbchevys idea about the custom thermac with headers. Guess I'll have to look into it more. Also, I already asked on a different thread but I'll ask here too: will shortly headers actually fit on a 100% stock 305 engine? Seems like there wouldn't be enough room for them...

 

[565bbchevy]

I did but I like bbchevys idea about the custom thermac with headers. Guess I'll have to look into it more. Also, I already asked on a different thread but I'll ask here too: will shortly headers actually fit on a 100% stock 305 engine? Seems like there wouldn't be enough room for them...

The thread I pulled that picture from the guy said that set up worked well and was much faster than the factory set up because headers create heat much faster since they are so thin.
As far as shorties I don't see any issues with fitting them the problem will be trying to attach it to your stock single exhaust and catalytic convertor, it might take some creative bending by the exhaust shop.

 

[LukeZ]

The thread I pulled that picture from the guy said that set up worked well and was much faster than the factory set up because headers create heat much faster since they are so thin.
As far as shorties I don't see any issues with fitting them the problem will be trying to attach it to your stock single exhaust and catalytic convertor, it might take some creative bending by the exhaust shop.

Cool, thanks a bunch. I'll post a picture of what I mean with my engine later on after work.