Lynn;  What are your thoughts on the Weber 48 collecting varnish.  Maybe a heat shield and a blast tube.  Or maybe MM oil going through will keep it clean or just gum it up.  Interesting, I have never seen a varnish problem.  On the other hand, when you burn the fuel out of the carb on the Lycoming at shutdown, the carb is hanging there on the hot oil pan.  JohnD

I use 87 or 93 octane street gas in the race car. At the end of each race, and sometimes at the end of a session, the tech people want a fuel sample. The heat under the hood of a stopped race car is such that the fuel boils out of the carb and floods the engine. It also boils in any exposed fuel line near the carb, pushing fuel into the carb over the needle and seat seal and after a while backwards through the sliding vane pumps. The fuel pressure gage goes nuts for a while.

 

So, I can crack the sample port and fill their little vile with no pumps turned on.

 

P.S. Fuel destroys Lexan instantly. If the Lexan has been stressed, as in bent into the shape of a windshield, it happens faster.

 

Since the carb does not need to be opened to change jets, the Drummond built carb is opened once each winter to remove anything that has slipped past one of the three filters. (Never anything but black dust from the fuel lines decomposing)

(normal). It has no varnish or any type of discoloration at all. None of them ever have.

Boiling the carb dry after each use must be close to the worst case situation.

 

So, if you cycle the carb idea every 50 hours, just to be sure it is still there, it would only have fuel in it for a few hours as it will boil out  and run bone dry between cycles.

 

You could rig the fuel control valve to the carb to activate the switch to run the low pressure pump for the carb,  Or, have the switch beside the valve control.

 

If the fuel tanks are higher than the carb, a vibrator pump could fail and you would still get enough fuel to get home. Just 3 or 4 pounds is plenty for a stock Weber. This is an idea that feels right to us old people who can see over 100 years of successful carburetor use, and only the mystical electronic stuff for a few years.

 

The carb is just slightly more complex than a toilet. How many successful hours do we have on toilets?

 

Lynn E. Hanover