Don't bomb it
I had a 82 volvo diesel. At about 140,000 miles head gasket went. It is 6 cyl volkswagen engine. Also, do not over tighten the rear cam belt to the injection pump as it will wear out the nose bearing in the pump.
You can advance the timing a little if in a warm climate, that is it.
These engines will break their cams too. Happens a lot.
The best way to get more power is to swap in a turbo diesel motor from a volvo 740 or 760. Much better. If yours is automatic, swap in the trans too the 740's used 4spd autos. The turbo motor is better design.
Same volkswagen 6 diesel is common industrial engine in european equipment. Parts are available if you know where to look. forget the volvo dealer.
I replaced my injection pump due to the nose bearing problem: Volvo dealer = $1,700, Volkswagen industrial, $1,100, Auto Zone! $875, Local diesel shop rebuild, $385.
P. S. Mine was 3 sped auto, 240. Best mileage was 26mpg

And the slowest car I ever driven. Way slower than my current 83 Jetta 5 speed.
Doug Rees
