Actually, this is the residue from the carbs on Andrew’s ’74 Midget, in this week for a five speed conversion.
It never ceases to amaze me how much crud gets into the float bowls of SU carbs, even with a filter installed. It seems that most float bowls have a bunch of silt at their low point, just waiting to be stirred up and to clog your needle and seat. If your carbs are prone to overflow, the silt you see in the pan could be the culprit. Now would be a good time to check inside your float bowls and make sure they are clean.
This picture also shows several other potential problem areas… notice the early plastic floats made before ethanol existed. Just like with plastic fuel sender floats, these plastic carburetor floats are subject to ethanol induced failure which will cause them to sink and also cause your carburetors to overflow. The solution is to use the nitrile floats (that we sell in our catalog) which you can find by clicking here (these are available for H1 and HS2 carbs)
In the photo, you can also see throttle butterflies that are equipped with emission control bypass springs. These were designed to reduce the amount of unburned fuel entering your tail pipe when the throttle is closed while the car is decelerating. You can see how someone soldered them shut, but they still leave a large wart in your carburetor throat, which can’t be fast. We put on new flat butterflies, which you can also find in our catalog by clicking here.
And lastly, I’ve been harping on Viton-tipped needles and seats for the carb float and these seem essential for increased reliability. Overall routine maintenance should include a check of your float chamber to make sure it doesn’t harbor the same quantity of rust particles you can see in this silver tray.
And most importantly you need a good clean fuel tank… it seems that a large percentage of the problems we encounter every day can be traced back to a fuel tank that is shedding rust (or even a previously coated fuel tank that is shedding its coating) and contaminating the float bowls, thereby diminishing reliability.