Here's the weight of the TT40 vs the 426 Jett with venturi:

1) The TT40 with back-plate mount, prop, and spinner nut weighs 19.5 ounces.
2) The Jett (venturi instead of carburetor) with back-plate mount, prop, and spinner nut weighs 17.2 ounces. This also requires a remote needle valve that weighs 0.4 ounces.
The 426 engine is a very forgiving racing engine that is used for 426 class racing. This class was very popular at this year's NATS.