Originally posted by Angus
Didn't later He 177's have 4 engines too.....I mean 4 props as well???
No, they did not. (well, in fact all 177´s had 4 engines)
The 4-engine, 2 prop layout was choosen because the Luftwaffe wanted to be the new heavy bomber to be capable of dive-bombing! (doctrine vs reality, hehe) Even before trials showed the problems of this configuration (see the posts above), Heinkel came up in 1938 with the proposal of producing a conventional 4-prop version, but his wish was denied by the Luftwaffe, for such a version could not dive bomb (well, they did not see our Lancaster in AH2...)
After the first few losses, Heinkel rebuilt a standard He 177 A-3 into 4prop configuration using 4 BMW 801 engines. This was done as a private venture without Luftwaffe support. As far as i know, there was only one prototype, but defenitely no serial production. In 1944 this project evolved into a planned He 277, a true "heavy bomber" with 4x 2000HP and a loaded weight of 42000kg.
Another spin-off was the He 274 high-altitude Bomber with 4 DB603 engines and a planned ceiling of 14000m The prototype was build by Farman in Suresnes near Paris, but of course the French were not in a hurry, and the Machine had it´s first flight well after the war...