BEagle,
The 1649 Constellation (same engines as the DC7 series) was a delight to fly, and was a bit faster that the DC7.
The engines, operated at normal cruise power, had a very delightful sound, and as they were mounted rather far outboard, were quieter than the DC6.
310 KTAS was not uncommon.
When 115/145 avgas disappeared, so did these aircraft, as they had to be operated in low blower only...and autorich, with lower octane fuel.
The power recovery turbines were a good idea, but tended to overheat, and as a result, had a rather short MTBF.