Re: 37, 120 carb percolation problems

Posted by 39SixSedanMan On 2012/8/4 9:28:39

For what it's worth, I had a very similar issue on my 39 Six with a Carter WA1.

Have you checked the integrity of the carb float? If the float has a hole and is sinking, the effective fill level will be higher than it should be. THe float is low, so the needle valve is open, pouring more fuel into the bowl. When the engine is running, it may not be noticed, especially if the idle speed and mixture have been recently adjusted, which may compensate and mask the issue. When the engine is shut down, the residual fuel line pressure between pump(s) and carb will just pour into the bowl and over the idle level port and right down into the hot manifold. The height relationship between float level and idle port flow circuit is critical.

Further, the car may be able to be restarted if done within a minute or so of shutdown, or once the car has time to clear the flood.

Before I determined that the issue was a sinking float, I checked the anti percolator function, other carb flow circuits, the idle, and all kinds of other things. Once repaired, all issues resolved.

It is possible to make solder repairs to a carb float, but I recommend having a pro do that unless you are skilled at low heat soldering. You don't want to change the weight of the float with globs of solder as it will affect the bowl fill level.

Hope this helps.
Pat