Ok, here goes. Got myself an '85 Z-28. The guy I bought it from says they took the original EFI 305 out and slapped a carbed 350 in it. While it does have a carb, the harmonic balancer is from a 305. Not 100% sure they are interchangeable. Also, NO NUMBERS... ANYWHERE. Not on the heads, block, nothing. You can feel the plate next to the bell housing, but it looks lie somebody filed the freakin numbers off. Anyways, back to my original point. I've got an AC/heater problem. Once the engine gets up to temp, smoke starts coming through the vents inside. It's not exhaust, but it does have a distinctive smell. If I stop, it doesn't come out at all, but once I hit the gas, it BELLOWS out. Not sure if it helps, but it makes the windshield fog like crazy. Anything Ya'll can think of will help.

 

does it smell sweet? to me it sounds like a leaky heater core. is the passenger floor board wet?

 

I can't really describe the smell. My friend had a heater core leak, and it smelled like maple syrup. That's not what I'm smelling, but you may very well be right. Could be a different type/mixture/ect. of fluid. How hard is replacing a heater core. I'm working with very basic hand tools and no garage.

 

Smoke bellerin outta the heat vents is a badly leaking heater core. Been there, had that. You'll want to replace it ASAP before it leaves you on the side of the road.
You can bypass the core (loop the heater hoses) for the time being, if you don't need heat.

 

Heat would be something useful, seeing as its only getting colder now. Autozone says a heater core is only $30, can probably get it fixed this weekend. It's been running like this for about two weeks. Not as bad as it was this morning, but I would see a little smoke here and there.

 

Be prepared for an all day job changing the heater core! They're a pain to get out!

 

2 weeks.....you're lucky! A few years ago I took one of my old Vettes to a car show. It went from me smelling antifreeze, to a little "smoke" from the vents, to literally filling the cabin with smoke, all within a 5 mile range. Made a pit stop at a gas station and looped the heater hoses, refilled the antifreeze, and was on my way again.
Tick...tick...tick..., that's the sound of your time running out quickly!

 

There not too bad to replace, but you do need to pull the dash. Expect it to take all day. I did one on my buddy's 90 bird.

 

Yay, the one thing I don't have tons of... time. Oh well. I can just loop the hoses for now. Just gotta find a nice diagram that shows how. Thanks for the help guys.

 

on the firewall towards the center there should be 2 black hoses, about 1" in diameter. the easiest way to bypass the heater core is to unhook the lines at the heater core and clamp them together with a connector.