86LG4T56

I've searched pretty hard and I can't find this.

What is it in the heads and intake manifold that prevents carb icing? Is it the exhaust crossover passage? Whatever it is, do the Edelbrock E-tec 170's have this? I want vortec shaped chambers, but I don't want to go fuel injected. I'm not worried about emissions. I believe the vortec shape burns clean and I'll keep my catalytic.

wesilva

iTrader: (35)

The exhaust crossover passage is one very big factor. I understand that in some cold regions of the country, the Air Gap series intake manifolds will experience this condition. Not sure if the E-techs have exhaust crossover.

five7kid

iTrader: (14)

To the best of my knowledge, no Vortec-style head has cross-over passages.

The cross-over passage wouldn't affect carb icing much, anyway. That's a function of air temperature and humidity, and carb temp as heated by the intake manifold. The cross-over passage goes under the plenum, and doesn't heat up the carb mount significantly. Some older factory manifolds brought the exhaust flow up by the carb, though (until they carboned closed, anyway).

If you want to prevent carb icing, use a thermovac air cleaner.

F-BIRD'88

Yes on factory cars the exhaust heat is routed up in the mnaifold under the carb to prevent iceing along with a heated air cleaner pickup at the exhaust manifold.

Vortec heads do not have a exhaust heat raiser passage but the Edelbrock Performer and RPM intake have a hot water passage under the plenum to heat the carb base.
The air gap intakes do not. You can plumb hot water from the heater hoses to run under the carb plenum on these manifolds for winter use.

86LG4T56

five7 do you think this is even something to be concerned about in this desert we live in?

five7kid

iTrader: (14)

Two nights ago when I left work to go home, the temperature was 17 degrees F and humidity 80%. The car started right up, drove down-hill for the first 1.3 miles (e.g., not much load to warm it up more quickly), didn't stumble at the stop sign at the bottom, basically ran fine the whole trip home. I haven't seen any problems whatsoever with icing in the 5 years I've driven this car, nor the last 3+ with headers that don't have the EFE valve.

So, no, I wouldn't worry about that. What I would worry about is getting past Colorado Air Care with Vortec-style heads.

F-BIRD'88, now I'm going to have to go look at my stock LG4 manifold (running the ZZ crate manifold now). I know the factory '66 396 manifold ran the exhaust up to the carb, but I was under the impression it only ran under the plenum in later years. Wouldn't surprise me if there are differences between US (aluminum) and Canadian (cast iron) manifolds, either.

SSC

We actually get colder air down here with the wind chill off our resivor and high humidity. Ive never had icing issues with the bird, out 3rdgen engine compartments keep heat traped this sucks durring the summer months. The only thing I had icing issues with was my truck when I was running a single pane, open element and edelcrap carb. Edelcraps run the coolest, too bad they suck soo much.

Apeiron

They do? I'm pretty sure my Performer RPM doesn't have such a thing, but it does have the exhaust crossover passage.

Or is this just a Vortec thing?

86LG4T56

I called the Edelbrock tech line. Hold time was like 15 minutes! But the guy said that as far as the vortec style intakes go, the RPM has this coolent passage for winter use, but his computer doesn't say that the performer or the air gap do. I didn't ask him if the regular RPM has it. He also said the E-tec doesn't have the exhaust crossover.

But the Vortec style RPM manifold doesn't come with the spread bore carb mount, which I need to keep my stock air cleaner assembly. He said there's an adapter that's 1/2" thick. Wonder if all this will clearance the hood?

five7kid

iTrader: (14)

How is it you're not worried about emissions?

Air_Adam

I had no problems about a month ago when it was -56*C outside. I have the heat passage on my intake blocked off, too. Its got a Holley 4bbl on top.

But like I said, it was -56*C outside, and it started up just fine and ran like normal once it warmed up a bit. No carb icing issues here. Thats with no thermovac air cleaner, no EFE valve in the exhaust, and a blocked heat passage in the manifold.

86LG4T56

All I'm getting rid of is the EGR and the computer carb, which I don't think will dirty me up too much. Besides, next year I get the "old car" plates, and then I don't have to do another inspection for 10 years, wahoo! It'll probably take me that long to save the $2500 for the short block, heads, cam, intake, carb, etc. But I always want to keep my visual inspection up and I'll always run the catalytic.

five7kid

iTrader: (14)

I'm not sure you've got all your facts straight.

The vehicle has to be 25 years old for "collector" plates, 1986 requirements in Colorado are tight enough to make getting past the sniffer with non-feedback systems very difficult, visual looks for little things like EGR valves and non-computer carbs, etc.

Good luck, though.

Apeiron

At -56 there probably isn't enough humidity for icing to be a problem. It's more likely to happen near freezing in damp weather.

I've never seen it happen though.

F-BIRD'88

Well ya know the temperture drops about 10* as soon as ya cross the border into Canada.....

I remember the old big block cast manifolds with the "heat track" right at the carb flange too. Some of the small block cast intakes had that too. Not sure about the LG4 cars specificly.
Carb icing is most likely to happen whe the temp is around 35 to 45*F wth high humidity.

When it's real cold, it doesn't seem to happen.
It's ususally in the late fall that people complain about this.