I was wondering what this capped metal vacuum line near the rear of the engine was for, and it took me taking my carb off (for a re-build) to see that it goes down to a heat riser on the left bank of the engine. So it's capped and obviously not functional... my question is: with no vacuum applied, is the default position of the baffle OPEN to allow exhaust to flow, or CLOSED to keep exhaust gases somewhat up in the engine to help with warm-up. There will come a time when this pesky little device will be removed when the exhaust is re-done, but for now I'm wondering if I need to hook it up to a manifold source to make certain the exhaust flows freely.

BTW, it's an 84 F250 with a 302

 

You sure you want to remove the heat riser valve? It's colder than ice in Buffalo during the winter...and this applies to both Buffalo NY & Buffalo WY

 

Don't remind me... LMAO

But actually, I don't drive the truck in the winter time. Maybe some fall weather (temperature wise) but I don't even drive the truck in the rain.

Also, none of the emissions are hooked up anymore but this was actually disconnected before I even got the truck. I'm just wondering if it's playing a small part in my acceleration problem because the exhaust isn't being vented properly.

 

Would it be possible for you to post a picture of it? If it's not being driven in the cold I believe it'll be ok but I want to be sure what you are referring to is exactly what I think it is.

 

I'll snap a picture of it an post in the morning. Just got in from work and it's a freaking t-storm out there right now.

 

Upper pic: Exhaust Control (aka Heat Riser) Valve.

 

That's the ticket! So anyone know what position the valve would be in with 0" of vacuum? I would assume closed.

 

If I remember correctly, the default position is open.