There is no question that the b21/23/230 represent advances over the B18/20 engines in design. What is surprising is that power ratings, even for slightly larger engines, were never significantly higher than for the B20.

At least in the US, we have not seen modified NA OHC engines producing more
power than the B20. Its comparatively easy to mofify a B20 to get power in the
130 - 160 HP range, with higher outputs from the larger displacement versions, so why go through all of the trouble and expense of doing an engine swap to an OHC engine for no increase in power? Essentially its a lot easier to modify the engine that's already in the car.

In some forms of racing, ITB for example, the 140 and 240 have been in the same class and the 140 has been by far the better performer.

Even in terms of turbo engines, the non intercooled B21s which were very nice performers in the 240s only produced 130 HP in stock form, easily equaled by a comparatively mildly modified B20. The intercooled turbo produced 160 HP, still in the range of what we can do with a NA B20.

As mentioned, adding our supercharger kit to a modified B20 will get you HP in the 200 + range, enough to satisfy most people, with less effort and probably expense than doing an engine swap. Certainly if your time is worth anything.

Utimately, I am sure that with the proper modifications, you can get more power from a turbo b230 or 234 than we can get from a B20 - basically because of a more efficient head design. But these engines seem to take quite a bit of modification to get them to last with power in the 200 - 300 range. So far we have run b18s and B20s with stock bottom ends up to 15 lbs boost without a failure. There are stories from Sweden of turbo drag racers being able to run higher boost with B20s before they came apart than the later engines.

If anyone has information on what has been achieved in terms of power with non turbo, modified OHC engines, that would add a lot to the discussion.

John
V-performance.com