why were some 4-cylinder cars designated 760? or 780? is this due to...the engine making as much power as an equivalent 6- or 8-cylinder engine?
similar to BMW's 745i from the 80s?

marketing-the 740s were cheaper than the 760s, even though they both could have a b230ft. the 780 was supposed to be the top of the line.

when the line was introduced in 83, they were both 760s. a b28 v6 and the a d24t. the 84 got a b23ft but it was still a 760. the 740s in 85 and later always had a 4, but the 760 could get anything except a non-turbo b230. the 780 was intro-ed with the b280 but the rep took it's toll and the b230ft was brought in. and so it goes, chuck.

hi there,
i can explaint he logic behind beemer and benz car tpe numbers but i don't know about the volvo numbers..
For beemer or benz numbers..
745i menas , it is a 7 series body and has 4.5 liter engine under the hood with injection..
for beemer numbers after the specifiys the spec.. for example C is coupe, L is usually luxury and long base..and for beemer M3, or M5 those r the special cars which r loaded with luxury and sporty goodies and has an higer out put engine than regular engines.. M3 has 3.0 liter engine,M5 5.0 liters...
For Mercedes for example C300 midicates that that car has a compact body stryle and 3.0 liters engine.. E usulay stands for injection, SL is sport luxury ect. ect... And don't forget the AMG branch of mercedes.. It indicates that that benz is special in everway..
Hope this kinda answers ur question , i hope somebody can help with the volvo numbers..
Sammy29926