Choke Coil story

[Steve L.]

A short time ago when my 73 just turned it's first birthday, I must have backed into a snowbank resulting in a muffler full of snow(that was my guess). A short time later after shuting the engine off for some time, I noticed that the get-up-and-go was sluggish. I also noticed that even when fully warmed up there was no exhaust coming out of the right side. This was in the dead of winter in Winnipeg( just north of Minniapolis).

So, I figured I would take it on the highway to "blow it out". That didn't do anything,,,,but the next time I started it, it ran really badly.

I popped the hood and looked around. To my amazement, the choke coil base (aluminum) had melted, pooled between the intake manifold channels and solidified, leaving me with no choke control.

The right side exhaust was plugged with ice and forced the exhaust through to the other side.

I found a heated underground garage and left it there for several hours, then I ran around town for awhile. That cured that problem. Still amazes me how hot that manifold got.

Steve L
73 coupe since new

[Joe L.]

Re: Choke Coil story

Steve----

Just one small correction: I believe that the choke coil base (choke stove) on your 73 is zinc-diecast ("pot metal") and not aluminum.

[Steve L.]

Re: Choke Coil story

Now that would make more sense, Al melts around 1200 deg f, while Zn(pure) is around 780 deg- acording to a quick look.

Steve L
73 coupe since new

[Michael W.]

Hmm, tall tales from the prairies

Steve,

Operating your car with a plugged muffler outlet (causing zero flow) would be no different than operating your car with a stuck heat riser valve. Both would force the right side exhaust manifold flow to go through the intake manifold (pre-heating the carb) and then out the left side manifold.

It's very common to see heat riser valves stuck closed (check the archives) and I've never heard of this causing a meltdown of an external engine component.

My '73 L48 with stock heat riser flows ONLY through the left pipe when cold, just like GM designed it to, and the Canadian Tire Motomaster Chevrolet orange paint on the intake manifold is barely discoloured.

[Craig S.]

Re: Choke Coil story

Steve - this problem can be cured by not living north of Phoenix AZ...Craig

[Steve L.]

Re: Hmm, tall tales from the prairies

Mike,
Your right, the exhaust goes through the intake manifold when the heat riser valve is cold or stuck. That's why I wasn't worried that I would cause any damage by driving with the right exhaust plugged.

But, I kid you not about the melted choke stove. As others have pointed out, it is not aluminum, but pot metal that has a much lower melting point.

I did floor it a few times hoping that the exhaust would clear itself out. That must have raised the temperature considerably. There was no visible change in the paint on the intake manifold even right under the melted puddle.

Steve L
73 coupe since new