MTFCA Forum

While putting the T away tonight I had the hood open and noticed the manifold was glowing red. Note; it seemed like it was only the last 3 cylinders also. I didn't have the car running very long either, I was just putting it away so I only went around the block. It did choke on itself a few times from a rolling start but it is still cold where I'm at and I didn't warm her up like I normally do. My guess is timing but thought I'd throw it out there in case there are a few educated guesses I can add to my investigation tomorrow.

Or running too lean.

Steve's right - that generally means you're running too retarded on the spark.

Here's the reason, as I understand it: If the spark ignites the fuel late, it's still in the process of exploding when the exhaust valve opens, and the explosion continues in the exhaust manifold - thus heating it red hot.

The biggest danger here, is that it will excessively burn the exhaust valve and seat.

This is a good reason to do a night-time run with the hood off. Experiment with different settings of the timing, and your passenger can see the manifold and tell you what's happening.

There's also the possibility of the mixture being too lean. I can't explain why that heats the manifold, without more space than I have here. It's counter-intuitive. You'd think that too much fuel would cause a hotter burn, but take the word of experience on this. While you're doing your night-time drive-around, you could fiddle with the mixture as well.

Running too lean; just heat/flame is coming out the valve no unburnt fuel to help cool the valve. Running a little richer, the unburnt fuel does help cool the valves as it passed into the manifold and helps from burning your valves.
But it could be ether or...

Just curious Jeff, carburetor or vaporizer?
A vacuum leak will cause it to run lean. Couldn’t hurt to check the nuts on the manifold and see if they are snug.