Wed Apr 10, 2013 11:50 am
If you want OEM look then go for a nice M20 in either 2.5 or 2.7/2.8.
The power expected from a 2.7 really depends on the head used, a 731 head really stunts the engine so bear in mind what head they have used when looking at power figures.
For a 731 2.7 around 180hp is normal and 190lb/ft, power will drop fast after about 5.5k as the inlet ports choke.
A 2.7/2.8 with the 885 head is around 190hp and the same torque, as the head flows a bit better the power hangs on to around 6k.
Fitting a cam to either (or porting the head which is a better fix) will see power over 200hp and torque around the same.
Fuel economy will be around the same as a 325 as the volumetric efficiency of the engine is better.
If you want more power and torque then go for an M5x in the same flavors as above, pretty much the same info but add 20hp to all the numbers.
If you want as much torque as an m30 without the fuel consumption then build a 3l M20 or a M5x 3l hybrid, both will be better engines than a stock M30.
The M30 is a really crude lump by modern standards, yes it makes north of 200hp standard but it does so by being 3.5l, they are heavy and thirsty and at best an early 70s design.
As nice as an E30 with an M30 in it is it really is a conversion that should be consigned to history, we have the larger M5x engines, the M6x engines and the v12 to fill the void of non stock engines and with options like that the M30 shouldn't even get a look in.
A stock M60B30 makes the same power and gives about twice the mpg of the M30, just look at the E34 535 vs 530 for example. (M60B30 215hp 214lb/ft, M30B35 218hp 225lb/ft, If we look at the M60B40 then its game over for the M30. The M5 also proves the M6x engines can build plenty of na power). The M60B30 returns ~25mpg and the equivilent M30B35 would be around high teens, both in a heavier E34.
Those that have done M6x swaps report high 20s to low 30s in an E30, the boat anchor would be luck to see mid 20s.
ETA - best not mention the M54B30 engine as it wipes the floor with the M30.