Doing a bit of experimenting the other day with my speedy tiger, trying to get the carb balanced. [&:] This is far more difficult than aero engines. Anyway when I looked at the amount of disturbance going on in the fuel tank due to the pressure link from the exhaust manifold I reasoned that when the tank gets low some of this hot gas is being pushed into the feed to the carb and causing erratic power bursts. The guy in the hobby shop said that this link was required and I tend to agree for aero use when you consider the thousand and one diffierent positions the aircraft gets into but in cars I have my doubts.
I disconnected the pressure link and blocked the outlet from the manifold and the car runs much sweeter now. Just leave the top of the tank open to atmosphere via the nipple that you normally take the pressure line to and run it. The engine will pull what fuel it needs assisted by the atmospheric pressure which is quite awesome anyway (14.7 lb sq ft) depending on altitude above sea level.
The other cause of air in the feed to the carb is via the priming pump. Seal this off. If you need to prime the line to the carb just attach a long piece of clean fuel tubing to the nipple mentioned above (top of tank) and blow gently taking care not to ingest any fuel 'cos it will poison you. [:'(]
Have a try at the above and see how much better your car operates.

Safe driving.

regards,


Chadz [8D]