What engine does a funny car use?

What engine does a funny car use?
Funny cars generally use V8 engines which are patterned after an engine that is (or was) available in a high performance car from Chrysler, Chevrolet or Ford.
However, the sport long ago reached such a high competitive level that no funny car can use an actual production engine block and have a hope of winning.
For example many funny cars use an engine patterned after the 426 cubic inch Hemi that was produced by Chrysler. This engine was available in very high performance versions of some Dodge and Plymouth models.
The version in funny cars use parts specifically designed to win - and survive the incredible stresses involved in this class of drag racing. The street version of the Hemi from the factory might have produced around 450 horsepower (measurements vary) while funny car engines may displace 500 cubic inches and produce 3,000 horsepower. The funny car engine only needs to last for one quarter-mile blast at a time, and it's perfectly normal disassemble, inspect, and replace major parts after every run.
So the basic architecture such as the cylinder spacing, angle of the two banks of cylinders (the "V" in V-8), the two rows of rocker arms in each head, the single camshaft and pushrod actuation of the valves and hemispherical combusition chamber shape that gives the Hemi its name -- all are clearly recognizable as developed from the Chrysler 426 Hemi. On the other hand, there may not be a single part that is appropriate for street use. Many racing parts are completely unsuited to street use. For example, engine block of a funny car may have no regular coolant passages. There is no radiator. This is fine for a quarter mile at a time but obviously would not make for a practical street engine.
"Big block" engine designs from GM and Ford can be used. I haven't been around NHRA racing for years, so this may be inaccurate. But for years the Ford and Chevy-based funny cars were very rare.
All "top fuel" (nitromethane burning) engines are equipped with a supercharger and fuel injection to accelerate the car as quickly as possible.
Top Fuel dragsters also use a very similar engine set up.
For more information check out NHRA.com, the home page for the National Hot Rod Association.
I hope this helps you.