Is there any formula or way to estimate increases in horsepower or torque after engine modifications based on improved acceleration times? Suppose a vehicle had an engine transplant, exchanging an engine with a known horsepower and torque for another engine with unknown horsepower and torque (which nevertheless peaked at about the same rpm). Could the improvement in 0-60 times be used to estimate the output of the replacement engine?

The reason for my curiosity is that I have a ~5,650 lb. Gelaendewagen that had a low-compression engine (M110, twin cam) designed for third-world countries' low octane gasoline. I just replaced it with a custom long block that was built following the engines found in the high performance Euro sedans -- it includes custom, high-compression pistons and high performance camshafts. The engine builder promised me a lot of performance improvement, but frankly, I didn't expect (or dare hope) as much as I'm seeing. When the truck was stilll fairly new, it had a 0-60 time of about 17-and-change seconds. With this new engine, with just a couple of thousand miles on the clock, I'm doing consistent 13 second 0-60's on the same road, and using the same timing and shifting techniques as I did before.

The engine originally had about 154 hp and 167 lb-ft torque, and I expected that the new engine would merely be similar to the regular 185 hp of the Euro SEL sedans (and both engines peak their hp and torque within a couple of hundred rpms of each other, so this shouldn't be a factor). However, I find it hard to believe that such a reduction in 0-60 times, from 17.5 (average) to around 13.1 seconds, can be explained by a mere 20% boost in power. The engine builder promised a hotter engine -- I think he underestimated his work, and I think that you can appreciate my curiosity in trying to estimate what my new engine is really putting out.

Is there any formula or relationship that can give such an estimate of the new power output? I hope that you can help me -- even a rough estimate is welcome. Thank you very much.