Comparing 500Hp to a 302 Ford engine to a 557 big block,
we see the 302 needs to rev to 6500RPM whereas the 557 hits it at 4000RPM.
Further the 302 would be describe as a racing engine, an you might just call the 557 a truck mill.
786Tq or 1.34Tq/CID
Peak Hp 860 @ 6200rpm
More CID takes a lot of cam to make RPM, but the torque peak will be much the same even if it occurs at a lower RPM
As CID goes up efficiency is impacted by friction so the Tq/CID number will be less.
A 632 can make 900Tq or 1.42Tq/CID
Long duration cam and lots of compression
This is a 454 making 1.31Tq/CID
It will be a milder big block to manage.
Add more CID and you can add a bigger head to make more power
While this motor has less CID, the Tq is up due to more compression and more cam duration which exchanges low RPM torque for higher RPM torque.
I want to illustrate that torque comes from CID
This over bore 350 is making 507Tq which means it produces 1.4Tq/CID which is very high and requires very fine tuning.
Any AFR head will make 1.3Tq/CID without much effort.
If you cam a motor more or less, you move the torque curve, but a glace at the Hp curve at a given RPM will give you a sense of what to expect.
This 434 is a great platform for a maximum torque small block.
If it were a 383, it would make the same Hp, but at a higher RPM,
but torque would be 507lbs/ft and therefore less likely to snap an axle.
On this page I will add dyno test results.
It will remain a work in progress.
I'm just one of many V8 engine builders in the US.
I would gladly buy a motor from many of them if I didn't build motors.
To start I'll show you some graphs from Airflow Research.