[Cliff R]

"One big part of the limited performance gain that build like the last one that Cliff posted about is this , in the rpm range where the motor is now down on torque numbers the motor is also reving up slower.

This has a big impact on accelerating the mass of the car number 1, and number 2 getting the motor up into its new higher rpm range power band fast.

It’s the average numbers that are produced in a motors intended power band that matter the most!

In terms of street strip performance the amount of time that a motor spends between 5000 and 5500 rpm is very small when you have the cars rear gears of in a ratio range that can be lived with on the street.

You still need a wide power band of near 3000 rpm from off idle.
Stuffing in a bigger cam with heads of a port volume that only comes into there own at 4000 rpm and then do so with only a 2000 rpm wide power band is a commonly seen pit fall that folks make"

Correct. We saw next to NOTHING going from a 228/235/112 cam to a 231/240/113 cam in terms of improvements in average power. It also didn't help that the RAIV cam has over 80 degrees of overlap so bleeding of a lot of cylinder pressure at lower RPM's. Even with that said take the exact same build and increase the compression ratio a FULL point or so and everything changes. The added compression trumps the losses from the larger cam, vacuum at idle improves, throttle response, power at low RPM's etc. It will run equally as well as the smaller cam/less compression engine everyplace and have some added upper mid-range and top end charge.

I've never much liked the RAIV cam in a 400 build with around 10 to 1 compression and "D" port heads. Those engines are "lazy". I get more complaints from that combo here to the shop than any other. Take the same engine, port the heads to 240-250cfm, increase the compression ratio into the 11 to 1 range and you'll be hanging on for dear life on your first test drive!........FWIW......