Overboring B21 to 96 mm [B23-sized Pistons]

[Volvo351]

Volvo built a 2.1 and 2.3 liter engine simultaneously so I figure it's unlikely they were cast as two different blocks. I know for marine use the AQ125 was a 2.1 liter and the AQ145 had the 96 mm bore. Later the 2.1 liter engine was dropped and 2.3 displacement became the "base" or single-carb engine, with a 2.5 liter engine being the twin-carb model.

So, a 2.1 liter block should have enough meat to go to 2.3 liters, right? And the 96 mm pistons should weigh the same?

[billofdurham]

Welcome to Matthew's Volvo Site.

I would think the block can be overbored to 2.3 litres, but can find no definite proof. The piston weight can differ depending on the piston used. The B21A, B21E and B21F pistons weighed 555 +/- 6 grams. The B21ET and B21FT pistons weighed 535 +/- 6 grams. The B23A, B23E type 2 and B23F pistons weighed 570 +/- 7 grams. The B23E type 1 pistons weighed 535 +/- 6 grams.

Bill.